Easily deployable interactive direct-pointing system and presentation control system and calibration method therefor

ABSTRACT

A method for controlling movement of a computer display cursor based on a point-of-aim of a pointing device within an interaction region includes projecting an image of a computer display to create the interaction region. At least one calibration point having a predetermined relation to said interaction region is established. A pointing line is directed to substantially pass through the calibration point while measuring a position of and an orientation of the pointing device. The pointing line has a predetermined relationship to said pointing device. Movement of the cursor is controlled within the interaction region using measurements of the position of and the orientation of the pointing device.

CROSS-REFERENCE TO RELATED APPLICATIONS

Priority is claimed from U.S. Provisional Application No. 60/575,671filed on May 28, 2004 and from U.S. Provisional Application No.60/644,649 filed on Jan. 18, 2005.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to devices for making presentations infront of audiences and, more specifically, to devices and methods formaking presentations for which interaction with the displayedinformation through direct-pointing is desired or for which verbalinteraction with the audience may be anticipated.

2. Background Art

Technology for presenting computer-generated images on large screens hasdeveloped to the point where such presentations are commonplace. Forexample, the software package POWERPOINT, sold by Microsoft Corp.,Redmond, Wash., may be used in combination with a so-called ‘beamer’ togenerate interactive presentation material and project for viewing by anaudience. Often, such presentations are held in rooms not specificallyequipped for the purpose of showing presentations, in which case use ismade of a portable beamer in combination with a so-called ‘laptop’computer. Under these circumstances the projection surface may be a wallof the room.

During a presentation it is desirable for the presenter to be able tomove freely in front of the audience while retaining the capability tointeract with the presentation and point to specific features on thedisplayed images. It would also be desirable for the presenter to beable to capture verbal comments made by members of the audience so as toamplify and/or play them back to the larger audience.

In general, interaction with a computer is often facilitated by pointingdevices such as a ‘mouse’ or a ‘trackball’ that enable manipulation of aso-called ‘cursor’. Traditionally, these devices were physicallyconnected to the computer, thus constraining the freedom-of-movement ofthe user. More recently, however, this constraint has been removed bythe introduction of wireless pointing devices such as the GYROMOUSE, asmanufactured by Gyration, Inc..

Broadly speaking, pointing devices may be classified in two categories:a) devices for so-called ‘direct-pointing’ and b) devices for so-called‘indirect-pointing’. Direct pointing devices are those for which thephysical point-of-aim coincides with the item being pointed at, i.e., itlies on the line-of-sight. Direct pointing devices include the so-called‘laser pointer’ and the human pointing finger. Indirect pointing devicesinclude systems where the object of pointing (e.g., a cursor) bears anindirect relationship to the physical point-of-aim of the pointingdevice; examples include a mouse and a trackball. It needs no argumentthat direct-pointing systems are more natural to humans, allowing fasterand more accurate pointing actions.

Indirect pointing devices known in the art include the following. U.S.Pat. No. 4,654,648 to Herrington et al. (1987), U.S. Pat. No. 5,339,095to Redford (1994), U.S.

Patent No 5,359,348 to Pilcher et al. (1994), U.S. Pat. No. 5,469,193 toGiobbi et al. (1995), U.S. Pat. No. 5,506,605 to Paley (1996), U.S. Pat.No. 5,638,092 to Eng et al. (1997), U.S. Pat. No. 5,734,371 to Kaplan(1998), U.S. Pat. No. 5,883,616 to Koizumi et al. (1999), U.S. Pat. No.5,898,421 to Quinn (1999), U.S. Pat. No. 5,963,134 to Bowers et al.(1999), U.S. Pat. No. 5,999,167 to Marsh et al. (1999), U.S. Pat. No.6,069,594 to Barnes et al. (2000), U.S. Pat. No. 6,130,664 to Suzuki(2000), U.S. Pat. No. 6,271,831 to Escobosa et al. (2001), U.S. Pat. No.6,342,878 to Chevassus et al. (2002), U.S. Pat. No. 6,388,656 to Chae(2002), U.S. Pat. No. 6,411,277 to Shah-Nazaroff (2002), U.S. Pat. No.6,492,981 Stork et al. (2002), U.S. Pat. No. 6,504,526 to Mauritz(2003), U.S. Pat. No. 6,545,664 to Kim (2003), U.S. Pat. No. 6,567,071to Curran et al. (2003) and U.S. Patent Application Publication No.2002/0085097 to Colmenarez et al. (2002). Each of the foregoingpublications discloses a system for which the 2 dimensional or 3dimensional position, orientation and/or motion of an object, such as ahandheld pointing device, are measured with respect to some referencecoordinate system using appropriate means. Such means include acousticdevices, electromagnetic devices, infrared devices, visible lightemitting diode (LED) devices, charge coupled devices (CCD),accelerometer and gyroscopic motion detectors, etc.. Although for someof the foregoing devices the reference coordinate system may bepositioned close to the display means, no information on the actualposition of the presentation display with respect to the system is used,causing the resulting pointing action to be inherently indirect and,hence, less natural to the human operators of such systems.

Other inherently indirect-pointing systems that do not require theposition or orientation of the pointing device to be known includedevices such as disclosed in U.S. Pat. No. 5,095,302 to McLean et al.(1992) and U.S. Pat. No. 5,668,574 to Jarlance-Huang (1997). Theforegoing patents describe indirect-pointing methods, that do notprovide the speed and intuitiveness afforded by direct-pointing systems.

Direct pointing devices are disclosed, for example, in U.S. Pat. No.4,823,170 to Hansen (1989), which describes a direct-pointing systemcomprising a light source, a position-sensing detector located adjacentto the light source and a focusing reflector that, in one application,is parabolic shaped and is attached to the pointing device.Additionally, procedures are described to calibrate the system. In theunderstanding of current applicant, however, the physical location ofthe position-sensing detector needs to be, at least preferably, adjacentto the display means. The system disclosed in the Hansel '170 patentcannot easily be ported to a room not specifically equipped for thissystem.

U.S. Pat. No. 5,929,444 to Leichner (1999) discloses a system primarilyintended for target shooting practice, but an application as adirect-pointing cursor control apparatus may arguably be anticipated.The system includes transmitting and detecting equipment in a fixedreference base and a moveable pointing device. A calibration routine isdescribed that aligns the detecting and transmitting means while keepingthe pointing device (i.e., a gun) aimed at the center of the target. TheLeichner '444 patent does not describe methods or means that allowdetermination of a point-of-aim of a pointing device on a target ofwhich the size and/or orientation have not been predetermined.Consequently, the system disclosed in the Leichner '444 patent is notsuitable to be used as a cursor control means for projection surfacesnot specifically adapted to be used with such system.

U.S. Pat. No. 5,952,996 to Kim et al. (1999), U.S. Pat. No. 6,184,863 toSibert et al. (2001) and US Patent Application Publication No.2002/0084980 to White et al. (2002) disclose direct-pointing systemswhere the 3 dimensional position and/or orientation of the pointingdevice is measured with respect to sources and/or detectors, thephysical position of which in relation to the display means is presumedknown. Such systems only work in rooms specifically equipped for theiruse.

U.S. Pat. No. 5,484,966 to Segen (1996) , U.S. Pat. No. 6,335,723 toWood et al. (2002) and U.S. Pat. No. 6,507,339 to Tanaka (2003) disclosemethods suitable for direct-pointing that are useful only if thepointing device is physically close to or touching the display area orvolume, for example used with so-called ‘interactive whiteboards’. Someof the foregoing patents describe appropriate pointer calibrationroutines. Such systems are not suitable for presentations where thedisplay surface is out of the presenter's physical reach.

U.S. Pat. No. 6,104,380 to Stork et al. (2000) discloses adirect-pointing system in which at least the 3 dimensional orientationof a handheld pointing device is measured by appropriate means.Additionally, a direct measurement is made of the distance between thepointing device and the displayed image. However, the system disclosedin the Stork et al. '380 patent does not include methods to ascertainthe position and orientation of the display means relative to thepointing device. In the foregoing system, these appear to be presumedknown. This is also the case for a system disclosed in U.S. Pat. No.4,768,028 to Blackie (1988), in which the orientation of ahelmet-mounted direct-pointing apparatus is measuredelectromagnetically. The foregoing systems therefore appear to beill-suited to operate in rooms not specifically equipped forpresentation purposes.

U.S. Pat. No. 6,373,961 to Richardson et al. (2002) discloses adirect-pointing system using helmet-mounted eye tracking means. Thepoint-of-gaze relative to the helmet is measured as well as the positionand orientation of the helmet relative to the display. The latter isaccomplished by equipping the helmet either with means to image sourcesmounted at fixed positions around the display or with means to image adisplayed calibration pattern. Of course, the foregoing system relies onsophisticated helmet mounted equipment capable of, among other things,tracking eye-movement. Moreover, such a system relies on an unobstructedline-of-sight with respect to the display and a substantially constantdistance from the display to the helmet-mounted equipment. The disclosedinvention does not lend itself to be easily used by a human operator inan arbitrary (not predetermined) presentation setting.

U.S. Pat. No. 6,385,331 to Harakawa et al. (2002) discloses a systemthat uses infrared technology in combination with image recognitionsoftware to distinguish pointing gestures made by the presenter, withoutthe need for an artificial pointing device. The disclosed system,however, requires the presentation room to be set up with highly tunedand sophisticated equipment, and is therefore not easily ported to adifferent venue.

U.S. Pat. No. 6,404,416 to Kahn et al. (2002) discloses adirect-pointing system where a handheld pointing device is equipped withan optical sensor. In such system either the display is required to beof a specific type (e.g., a cathode ray-based display that uses anelectron beam) or the displayed image is required to be enhanced bytimed and specific emanations. When pointed to the display, a handheldpointing device may detect the electron beam or the timed emanations,and the timing of these detections may then be used to ascertain thepoint-of-aim. The disclosed system is somewhat similar to thetechnologies used for so-called light guns in video games as disclosed,for example, in U.S. Pat. No. 6,171,190 to Thanasack et al. (2001) andU.S. Pat. No. 6,545,661 to Goschy et al. (2003). Of course, such systemsrequire either a specific display apparatus or a specializedmodification of the displayed images. Moreover, an uncompromisedline-of-sight between the pointer and the display is a prerequisite forsuch systems.

U.S. Patent Application Publication No. 2002/0089489 to Carpenter (2002)discloses a direct-pointing system that, in one embodiment, positions acomputer cursor at a light spot projected by a laser-pointer. The systemrelies on the use of an image-capturing device to compare a capturedimage with a projected image. As such, the system disclosed in the '489application publication makes use of calibration routines in which theuser is required to highlight computer-generated calibration marks withthe laser pointer. The system disclosed in the '489 patent applicationpublication is not unlike a system disclosed in U.S. Pat. No. 5,502,459to Marshall et al. (1996). Also, U.S. Pat. No. 5,654,741 to Sampsell etal. (1997), U.S. Pat. No. 6,292,171 to Fu et al. (2001), U.S. PatentApplication Publication No. 2002/0042699 to Tanaka et al. (2002) andU.S. Patent Application Publication No. 2002/0075386 to Tanaka (2002)all disclose systems that can detect a light-spot using optical means.Such systems specifically generally require the use of computationallyexpensive image processing technologies. All of these inventions requirea projection surface with adequate diffusion properties, as well as someform of optical system with a steady and uncompromised view of thedisplay area. As such, they limit the freedom-of-movement of thepresenter and place limitations on the position and opticalcharacteristics of the necessary equipment. Also, in some of theseinventions fast and involuntary movement of the user's hand may resultin a cursor that does not move smoothly or a cursor that does notperfectly track the light spot, causing possible confusion with theuser.

Other pointing systems known in the art may be classified as other thanentirely direct-pointing or indirect-pointing systems. Such systemsinclude one disclosed in U.S. Pat. No. 6,417,840 to Daniels (2002),which is combination of a cordless mouse with a laser pointer. Althoughthis system incorporates a direct-pointing device (i.e., the laserpointer), the method used by the system for interacting with thepresentation is indirect (i.e., by means of the mouse) and thereforedoes not afford the fast and more accurate interactive pointing actionsprovided by some other direct-pointing systems described in some of theforegoing publications.

Another system known in the art that uses both direct andindirect-pointing methods is described in U.S. Pat. No. 6,297,804 toKashitani (2001). The disclosed system is a system for pointing to realand virtual objects using the same pointing device. In the disclosedsystem, the pointing means switch between a computer controlled lightsource (e.g., a laser) and a conventional computer cursor, depending onwhether or not the user's intended point-of-aim has crossed a boundarybetween the real and virtual display (i.e., computer-displayed imagery).Various methods are described to establish these boundaries. Althoughthe computer-controlled light source may be regarded as pointing in adirect manner, its point-of-aim is essentially governed by the systemoperator using an indirect-pointing system such as a mouse. Thus, thedisclosed system does not allow for the desired flexibility afforded bytruly direct-pointing methods.

Other systems known in the art include those such as disclosed in U.S.Pat. No. 5,796,386 to Lipscomb et al. (1998), which discloses acalibration procedure to establish the relation between coordinatesystems associated with a handheld device and, in one embodiment, adisplay unit. The system disclosed in the Lipscomb et al. '386 patentmay arguably be applicable as a direct-pointing cursor control system.The disclosed calibration routine requires the user to register at leastthree 3 dimensional positions of the handheld device with a centralprocessing unit. The disclosed system does not appear to includecalibration methods for the case where the display unit is out ofphysical reach of the system operator. The system is thus not practicalfor use at an arbitrary venue.

U.S. Pat. No. 6,084,556 to Zwern (2000) discloses a head-mounted displayunit that displays information governed by the orientation of theapparatus, as measured by a tracking device. This way, the systemcreates the illusion of a large virtual display that is being looked atby the system operator. Of course, the large display alluded to does notconstitute a projected presentation. Also, no methods are disclosed inthe Zwern '556 patent to establish the relative position of thehead-mounted apparatus with respect to the display.

U.S. Patent Application Publication No. 2002/0079143 to Silverstein etal. (2002) discloses a system in which the position of a moveabledisplay with respect to a physical document is established. The '143patent application publication describes calibration routines in whichthe user is required to activate a registration button when the moveabledisplay is over some predetermined position on the physical document.The disclosed system only relates to 2 dimensional applications and,moreover, cannot be used in situations where the interaction region isout of the system operator's physical reach.

U.S. Pat. No. 5,339,095 to Redford (1994) discloses an indirect-pointingsystem where the pointing device is equipped with non-directionalmicrophone. Also, U.S. Pat. No. 5,631,669 to Stobbs et al. (1997)discloses the inclusion of a non-directional microphone unit in anindirect-pointing device.

SUMMARY OF THE INVENTION

One aspect of the invention is a method for controlling a parameterrelated to a position of a computer display cursor based on apoint-of-aim of a pointing device within an interaction region. Themethod includes projecting an image of a computer display to create theinteraction region. At least one calibration point having apredetermined relation to the interaction region is established. Apointing line is. directed to substantially pass through the calibrationpoint while measuring a position of and an orientation of the pointingdevice. The pointing line has a predetermined relationship to saidpointing device. The parameter related to the position of the cursorwithin the interaction region is controlled using measurements of theposition of and the orientation of the pointing device.

Another aspect of the invention is a method for controlling a computerdisplay cursor in an interaction region. According to this aspect, themethod includes establishing a calibration point having a predeterminedrelation to the interaction region. At least one of a position andorientation of a pointing line is first measured while directing thepointing line to substantially pass through the calibration point. Thefirst measurement is used to constrain a parameter of the calibrationpoint. The pointing line has a predetermined relationship to at leastone of position and orientation of a pointing device. A characteristicfeature of the interaction region is used to establish a property of acommon point of the pointing line and the interaction region measuredrelative to the interaction region. At least one of position andorientation of the pointing device is measured, and the characteristicfeature of the interaction region and measurement of the pointing deviceare used to control the cursor on a computer display image.

Another aspect of the invention is a method for controlling a parameterrelated to position of a cursor on a computer screen image. The methodaccording to this aspect includes measuring a first angle between apointing line and a first line, and measuring a second angle between thepointing line and a second line. The first line is related in apredetermined way to a geographic reference, and the second line isrelated in a predetermined way to a geographic reference. The pointingline has a predetermined relation to said pointing device. A firstparameter related to the first angle, and a second parameter related tothe second angle are used to control the parameter of the cursor on saidcomputer screen image, whereby the cursor position parameter iscontrolled by movement of the pointing device.

Other aspects and advantages of the invention will be apparent from thefollowing description and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a pointing device and base station according to a firstembodiment.

FIG. 2 shows a presentation venue and computer screen.

FIG. 3 shows program steps for selection of appropriate assumptionsaccording to embodiments 1, 2 and 3.

FIG. 4 shows program steps for construction of information set accordingto a first embodiment.

FIG. 5 shows program steps for ascertaining necessary 3D data accordingto a first embodiment.

FIG. 6 shows program steps for control of pointing device elements andcomputer cursor according to several embodiments.

FIG. 7 shows one example of a first embodiment.

FIG. 8 shows a second example of one embodiment of the invention.

FIG. 9 shows a third example of one embodiment.

FIG. 10 shows a pointing device and base station according to a secondembodiment.

FIG. 11 shows program steps for construction of information setaccording to a second and third embodiment.

FIG. 12 shows program steps for ascertaining necessary 3D data accordingto the second embodiment.

FIG. 13 shows a pointing device and base station according to a thirdembodiment

FIG. 14 shows program steps for ascertaining necessary 3D data accordingto the third embodiment.

FIG. 15 shows projection of interaction structure on horizontal andvertical planes.

FIG. 16 shows a presentation device according to a fourth embodiment.

FIG. 17 shows program steps for sound recording and playback accordingto the fourth embodiment.

FIG. 18 shows an image of calibration point and light spots at thepoints-of-aim.

FIG. 19 shows an alternative embodiment of pointing device.

FIG. 20 shows a prior art: construction of method M for a quadrangle.

DETAILED DESCRIPTION

A first embodiment of the invention will be described with reference toFIG. 1. A pointing device 20 has associated with it a coordinate systemx′ y′ z′. A portable base station 30 has associated with it a coordinatesystem x y z. Pointing device 20 and base station 30 may be equippedwith coordinate sensing devices, 201 and 301, respectively, that enablemeasurement of the 3 dimensional position and 3 dimensional orientationof pointing device 20 and, therefore, of a pointing line 21 (see alsoFIG. 2) that substantially intersects pointing device 20, all measuredrelative to the x y z coordinate system. Pointing line 21 maysubstantially coincide with the long axis of pointing device 20. Forexample, coordinate sensing devices 201 and 301 may be electromagnetictracking devices, such as the 3SPACE FASTRAK® system, manufactured byPolhemus, a Kaiser Aerospace & Electronics Company, Colchester, Vt.Alternatively, coordinate sensing device 201 and 301 may be based onultrasonic tracking systems such as those used in the LOGITECH 2D/6Dcomputer mouse, commercially available from Logitech Inc., Fremont,Calif. Other embodiments for coordinate sensing device 201 and 301 mayinclude, without limitation, sensors based on LEDs, CCDs,accelerometers, inclinometers, gyroscopes, compasses, magnetometers,etc. Also, combinations of such different types of sensors may be usedto acquire redundant measurements for quality control purposes. Forexample, a controlled-source electromagnetic position tracking systemmay be combined with compasses and inclinometers. Those skilled in theart will appreciate that independent measurements of the Earth'smagnetic field and gravity may be used to enhance the measurements madeby a controlled-source position detecting system. In the invention, anysystem may be used that is capable of determining at least parts of theorientation and position in three dimensions, with respect to coordinatesystem x y z, of a line-segment that substantially intersects pointingdevice 20.

Base station 30 may comprise a plurality of related physical entities,such as described in U.S. Pat. No. 6,608,668 to Faul et al. (2003); forclarity of explanation one of these physical entities will be associatedwith coordinate system x y z and be denoted as base station 30, thecenter of which substantially coincides with the origin of coordinatesystem x y z. For purposes of explanation of the invention, the originof coordinate system x′ y′ z′ substantially coincides with the center ofpointing device 20, and the z′-axis is substantially aligned with thelong axis of pointing device 20.

Pointing device 20 may also be provided with a light-beam projector 202,for example a laser. The physical position and orientation of theprojected beam of light with respect to coordinate system x′ y′ z′ maybe established with suitable accuracy at the place of manufacture of thepointing device 20 and may be presumed to be known. For purposes ofexplanation, the beam of light from the light beam projector 202substantially coincides with the z′-axis. Additionally, one or morecontrol buttons 203 a, 203 b or the like may be provided, as well ascommunication and control device 204. Communication and control device204 may be used to control various features of pointing device 20 andmay also communicate via wire, or wirelessly, with base station 30and/or a central processing unit (not shown separately), such as aCOMPAQ Armada M700 as manufactured by Hewlett Packard Company, PaloAlto, Calif. The central processing unit may also control a presentationwith which user interaction is desired. For clarity of the descriptionwhich follows, the central processing unit will be referred tohereinafter as “the computer.” Furthermore, pointing device 20 mayinclude an internal power source 205, for example a battery, or insteadmay be connected such as by wire to an external power source.

In addition to coordinate sensing device 301, base station 30 may beprovided with communication and control device 304. Communication andcontrol device 304 may be used to control various features of basestation 30. Communication and control device 304 may communicate withpointing device 20 and/or with the computer (not shown) that may controlthe presentation images. The communication and control device 304 mayuse wire- or wireless technology. In the present embodimentcommunication with the computer occurs via a universal serial bus (USB)compatible device or the like (not shown). Communication and controldevice 304 may communicate wirelessly with a relay device (not shown)that communicates via a USB compatible device or the like with thecomputer (not shown) that may control the presentation with whichuser-interaction is desired. There may be visible markings 302 on basestation 30 that indicate the orientation of one or more coordinateplanes defined by prescribed relations between coordinates x, y, z, aswell as features of the position of the origin of the x y z coordinatesystem. For example, a line may be used to indicate the z-x-plane of thex y z coordinate system, for which the y-coordinate is zero; anotherline may be used to indicate the z-y-plane, for which the x-coordinateis zero. Base station 30 may be provided with a level-sensing device 303to determine whether or not one of the coordinate planes of coordinatesystem x y z is substantially horizontal. Level-sensing device 303 maymeasure two angles or equivalent characteristics that define theorientation of one of the coordinate planes of coordinate system x y zwith respect to a horizontal surface. Level-sensing device 303 can be adevice such as disclosed in U.S. Pat. No. 6,466,198 to Feinstein (2002),which makes use of model ADXL202 accelerometers sold by Analog DevicesInc., Norwood, Mass. The disclosed accelerometers provide tilt angleinformation depending on their inclination relative to Earth's gravity.It will be apparent to those skilled in the art that many other types ofsensors may be used as embodiment for level-sensing device 303, forexample, capacitance-type bubble levels. See, for example, U.S. Pat. No.5,606,124 to Doyle et al. Finally, base station 30 may be equipped witha power source 305, for example a battery, or may have a connection toan external power source.

Referring to FIG. 2, a projection device 40 is arranged to project animage 50 generated by, for example, the computer (not shown). Theprojection device 40 may be used to generate a projection image 70 on aprojection region 60. For example, projection device 40 may be a 2000lumen projector, model XL8U, manufactured by Mitsubishi Corp. Projectionregion 60 may be a surface, such as a wall or a projection screen. Theprojection region 60 may define a flat plane or a may define a moreelaborate 2 dimensional (2D) or even 3 dimensional (3D) structure. InFIG. 2, projection region 60 is shown as a screen, but this is only forpurpose of illustrating the principle of the invention and is notintended to limit the scope of the invention. Alternatively thecombination of projection device 40 and projection region 60 may beincorporated in one and the same physical device, such as a televisionreceiver (cathode ray tube display), liquid crystal display (LCD) screenor the like.

There is a region of space that is designated as a region on whichinteraction with the user is desired. This region is denoted as theinteraction region 71. The interaction region 71 may be flat (planar) ormay be a more elaborate 2D or even 3D structure. The interaction region71 may have features in common with projection image 70 and may beassociated in some way with a computer screen interaction region 51. Inthe present embodiment, however, it will be assumed that interactionregion 71 or a scaled version thereof, is substantially part of orsubstantially coincides with projection image 70. Moreover, it will beassumed in this embodiment that interaction region 71 substantiallycoincides with the projection of computer screen interaction region 51as projected by projection device 40.

For display systems which include a separate projection device 40 andprojection region 60, the optical axis of projection device 40 may notbe aligned with any vector normal to projection region 60. Moreover,projection region 60 may not be flat and therefore may not even be a 2Dshape. Consequently, projection image 70 and interaction region 71 mayin general not be flat or rectangular, even if the imagery generated bythe computer is scaled so as to be presented in rectangular form. Inthis embodiment, however, it is assumed that projection region 60,projection image 70 and interaction region 71 are substantially flat.Furthermore, it is assumed in this embodiment that interaction region 71is substantially a quadrangle and that the associated computer screeninteraction region 51 is substantially rectangular.

Additionally, calibration points 721 a, 721 b, 721 c, 721 d may beprovided that may define characteristic features of interaction region71. For example, interaction region 71 may be trapezoidal in shape, inwhich case calibration points 721 a, 721 b, 721 c, 721 d may definecorners of interaction region 71 or corners of a scaled version thereof.Furthermore, screen marks 521 a, 521 b, 521 c, 521 d may be provided,and may but need not be associated with calibration points 721 a-721 dFor example, calibration points 721 a-721 d may coincide with theprojected versions of screen marks 521 a-521 d and may in this way beidentified by projection device 40. Calibration points 721 a-721 d mayalso be identified by other means than projection, for example by uniquedescriptions such as the ‘upper right corner of interaction region 71’,‘center of interaction region 71’ etc.

The operation of the present embodiment will now be described withreference to FIGS. 1, 2 and 3. A display system is set up at the venuewhere a presentation is to made, which can be a combination of aportable projection device 40 and projection surface 60, for example awall. The display system is connected, using appropriate interconnectiondevices, to the computer (which may be in the base station 30 or locatedelsewhere) that generates the presentation images.

The system user positions base station 30 at a convenient location,preferably not far from where the user intends to make the presentationdisplay. The user may position base station 30 in such a way that one ofthe coordinate planes of the x y z coordinate system is substantiallyparallel or substantially coincident with projection region 60. Thevisual markings 302 may assist in such positioning. Subsequently, theuser connects base station 30 to the computer (not shown), for examplevia a USB compatible device connection (not shown), or using a wirelessrelay device (not shown). The computer may be disposed in the basestation 30 in some embodiments. In some embodiments, the computer mayrecognize the base station connection and start a program, part of whichmay be contained in the communication and control device 304, incommunication and control device 204, or in control logic contained inthe wireless relay device (not shown). Alternatively, the user may berequired to load the program into the computer manually via a CD-ROMdrive, a floppy drive, memory stick (USB mass storage device—not shown)or the like. However it is loaded into the computer, the program mayinitiate a calibration routine that has as its object establishment ofthe shape, position, size and orientation of a defined interactionstructure 72 relative to the x y z coordinate system. The interactionstructure 72 is assumed to substantially coincide with interactionregion 71. The operation of the program will now be explained withreference to FIG. 3.

At 80 a the program is initiated. During step 80 b a default assumptionis made regarding interaction region 71. Specifically, interactionregion 71 is assumed to substantially coincide with a well-definedinteraction structure 72 (FIG. 2 shows an interaction region 71 and aninteraction structure 72 that are clearly not identical; this differenceis however only meant as an example, and as a practical matter ispreferably as small as possible). At 80 b default values are entered forthe orientation and position of this interaction structure 72. Forexample, the default setting may assume interaction region 71 tosubstantially coincide with an interaction structure 72 that is a (flat)quadrangle positioned in a vertical plane that substantially intersectsthe origin of the x y z coordinate system associated with base station30. As another example, the default setting may provide that interactionregion 71 substantially coincides with an interaction structure 72 thatis an isosceles trapezoid of which the parallel edges are horizontal andof which the position is unknown. Using such default values, calibrationpoints 721 a-721 d not only define characteristic features ofinteraction region 71 but also of interaction structure 72.

At 80 c a decision is made whether the default values for interactionregion 71 and interaction structure 72 should be accepted or overriddenby the user. In making this decision, input from level-sensing device303 and visible markings 302 on base station 30 may be used. If thedefaults are to be accepted, the program continues to 80 j, the detailsof which are explained below with reference to FIG. 4. If the defaultsare overridden, the program continues at 80 d to 80 i, during each ofwhich the user may override any of the default settings. The user may beaided during any of 80 d to 80 i by a library of predetermined shapes,predetermined orientations and/or predetermined positions, or the usercan be provided by the program with the capability to construct customshapes, orientations and/or positions. In any case, the programcontinues to 80 j.

It will be appreciated by those skilled in the art that once anassumption has been made regarding the shape of interaction structure72, it is possible to construct a set of three dimensionally distributedpoints in space that completely determines the 3D position, orientationand size of the interaction structure 72. The number of points in theset will depend on the complexity of the assumed shape and the ingenuitywith which the points are chosen. For example, a rectangular shape thatis arbitrarily oriented in space is completely determined by a set of 3points that coincide with 3 of its corners, but is also completelydetermined by a set of 8 points, pairs of which may determine each ofthe four edges of the rectangle.

Referring to FIG. 4, describing details of program element 80 j, thecomputer program continues at 90 a, at which a set P is generated thatincludes a quantity n of points in space, each represented as C(i)(0<i<n+1), that uniquely determine interaction structure 72, togetherwith descriptions of their roles in determining this structure. Forexample, if the program elements outlined in FIG. 3 reveal thatinteraction region 71 is assumed rectangular, set P may hold threepoints described as the upper-left corner, the lower-left corner and theupper-right corner of a rectangular interaction structure 72. If,alternatively, the projection of computer screen interaction region 51is substantially rectangular, and this projected rectangle has the samecenter but is physically two times smaller than interaction structure72, the three points may be described as the upper-right corner, thelower-left corner and the lower-right corner of a rectangle that has thesame center but is two times smaller than interaction structure 72.Thus, by carefully choosing the points in set P together with theirdescription, any interaction structure 72 may be completely determined.

In addition to set P, a 3D point CA and another 3D point CB aredetermined at 90 a. These additional 3D points are determined so as tolie away from interaction region 71, that is, they lie at some distanceout of the plane that is closest to or substantially containsinteraction region 71. The distance may be comparable to an edge ofprojection image 70. For example, point CA may be determined to lie nearprojection device 40 and point CB may be determined to lie at a distancefrom point CA that may be equal to the distance between projectiondevice 40 and projection surface 60, measured substantially parallel toprojection surface 60. Other choices for point CA and point CB may alsobe used. Additionally, sets A and B are generated during step 90 a. SetA includes a number n of lines A(i), each of which connects point CA toone of the points C(i) (0<i<n+1) in set P. Likewise, set B holds anumber n of lines B(i), each of which connects point CB to one of thepoints C(i) (0<i<n+1) in set P. Finally, at 90 a, counters a, b are bothinitialized to the value of n.

Flow then continues on to step 90 b, where a decision is made whetherthe program elements outlined in FIG. 3 have revealed any information onthe 3D position and orientation of interaction structure 72. If thedecision is positive flow continues to step 90 c, where this informationis used to establish a priori relationships between the coordinates ofthe points in set P. For example, the steps outlined in FIG. 3 may haverevealed that interaction structure 72 is assumed to coincide with thex-z plane, in which case the a priori relationships may include therequirement that the y-coordinates of all points in set P are equal tozero. A pre-set library of a priori relationships may be provided to aidin the execution of this program element.

The program continues to 90 d, which may also be reached from 90 b ifthe decision at 90 b is negative. At 90 d, line B(b) is removed from setB, after which counter b is decremented by 1.

The program continues to 90 e, where a decision is made whether complete3D information on the lines in sets A and B, together with a prioriinformation, constitutes enough information to uniquely determine thecoordinates of all the points in set P. For example, the programelements outlined in FIG. 3 may have determined that interaction region71 is assumed to be rectangular, but no information is known regardingits orientation or position. In this case set P may contain threepoints, corresponding to three corners of a rectangular interactionstructure 72. Each point C(i) (0<i<4) in set P would then be uniquelydetermined by the intersection of a line from set A and a line from setB if and only if sets A and B contained three lines each.

If the decision at 90 e is negative, the program continues to 90 f,where line B(b+1) is added once more to set B.

If the decision at 90 e is positive, program flow continues to 90 g. Theprogram flow may also continue from 90 f to 90 g. At 90 g a decision ismade whether counter b has reached zero, in which case the lines left inset B (which number may be equal to zero) are deemed necessary forunique determination of the coordinates of all the points in set P. Ifthe decision at 90 g is positive, program flow continues to 90 h. If thedecision at 90 g is negative, program flow reverts to 90 d.

During 90 h, line A(a) is removed from set A, after which counter a isdecremented by 1. Program flow then continues to 90 i, where a decisionis made whether complete 3D information on the lines in sets A and B,together with the a priori information, constitute enough information touniquely determine the coordinates of all the points in set P.

If the decision at 90 i is negative, program flow continues to step 90j, where line A(a+1) is added once more to set A.

If the decision at 90 i is positive, program flow continues to step 90k. The program flow also continues from 90 j to 90 k. At 90 k, adecision is made whether counter a has reached zero, in which case thelines left in set A (which number may be equal to zero) are deemednecessary for unique determination of the coordinates of all the pointsin set P. If the decision at 90 k is negative, program flow reverts to90 h. If the decision at 90 k is positive, program flow continues to 90m, the details of which are described with reference to FIG. 5.

In FIG. 5, the program continues to 100 a, where counter p isinitialized to 1 and variable n is set to the number of points in set P.

Program flow then continues to 100 b where a decision is made whetherline A(p) (connecting point CA to point C(p)) is included in set A. Ifthe decision is negative, program flow continues to 100 c, where counterp is incremented by 1.

If the decision at 100 b is positive, program flow continues to 100 e,at which the program identifies point C(p) to the user and then canquery the user to highlight this point using light-beam projectiondevice 202, preferably from a position such as point CA, as determinedpreviously at 90 a (FIG. 4). The user can also be queried to affirm thehighlighting action by, for example, activating one of the buttons 203 aor 204 b, or the like. The identification of point C(p) may occur, forexample, by having the program display a visible screen mark 521 a-521 dat a position on computer screen interaction region 51 associated withC(p), which may then be projected by projection device 40 to coincidewith point C(p). Other means of identification are also possible, suchas the characterization of point C(p) as ‘upper-right corner’ or thelike.

Program flow then continues on to 100 f, where the program can waituntil the highlighting action is affirmed by the user, after which the3D orientation of the z′-axis and the 3D position of the z′=0 point (ofthe z′-axis) are measured with respect to the x y z coordinate system,using coordinate sensing device 201 and 301, and communicated to thecomputer using communication and control device 204 and/or 304. This 3Dorientation and position is then associated with line A(p) and stored inmemory. Program flow then continues to 100 c.

After 100 c program flow continues to 100 d where a decision is madewhether p is equal to n+1. If the decision is positive, it can beconcluded that all necessary data on lines A(p) have been ascertainedand program flow can continue to 100 g. If the decision at 100 d isnegative, program flow reverts to 100 b.

At 100 g a decision is made whether set B is empty. If the decision ispositive, it can be concluded that enough information to uniquelydetermine the 3D coordinates of all the points in set P is contained inthe a priori relationships combined with the available data on the linesin set A, and program flow continues to 100 p. If the decision at 100 gis negative, program flow continues to 100 h.

At 100 h counter p is again initialized to 1. The user is subsequentlyrequired to reposition the pointing device 20 to a different location,displacing it substantially parallel to projection region 60 over adistance substantially equal to the distance between projection region60 and his or her present location. Other locations may also be used.

Flow then continues to 100 i where a decision is made whether line B(p)(connecting point CB to point C(p)) is included in set B. If thedecision is negative, program flow continues to 100 j where counter p isincremented by 1.

If the decision at 100 i is positive, program flow continues to 100 m,at which point the program identifies point C(p) to the user and canquery the user to highlight this point using light-beam projectiondevice 202. The program can also query the user to affirm thehighlighting by, for example, activating one of the buttons 203 a or 204b or the like. The identification of point C(p) may occur, for example,by having the program display a visible screen mark 521 a, 521 b, . . .at a position on computer screen interaction region 51 associated withC(p), which may then be projected by projection device 40 to coincidewith point C(p). Other means of identification are also possible, suchas the characterization of point C(p) as ‘upper-right corner’ or thelike.

Program flow then continues to 100 n, where the program may wait untilthe highlighting action is affirmed. After affirmation, the 3Dorientation of the z′-axis and the 3D position of the point z′=0 (of thez′-axis) are measured with respect to the x y z coordinate system, usingcoordinate sensing device 201 and 301, and are communicated to theprogram using communication and control device 204 and/or 304. The 3Dorientation and position are then associated with line B(p) and can bestored in memory. Program flow then continues to 100 j.

After 100 j program flow continues to 100 k where a decision is madewhether p is equal to n+1. If the decision is positive, it is concludedthat all necessary data for lines B(p) has been ascertained and programflow continues to 100 p. If the decision is negative, program flowreverts to 100 i.

At 100 p it is concluded that the combined information of the a priorirelationships and the data for lines in sets A and B that is stored inmemory is enough to establish the coordinates of all points in P, as isfurther explained with reference to FIG. 6.

Referring to FIG. 6, as will be appreciated by those skilled in the art,at 110 a the available information contained in the a priorirelationships and the orientations and positions of the lines in sets Aand B may be used to establish the coordinates of each of the points inset P, all measured with respect to the x y z coordinate system. It mayhappen that the 3D data associated with lines A(p) and B(p) (1<p<n+1)cause them not to intersect at point C(p); for example, this could bethe case due to insufficient accuracy in determining the orientationsand positions of lines A(p) and B(p). Under such circumstances pointC(p) may be estimated or determined in such a way that it lies halfwayalong the shortest line-segment that connects lines A(p) and B(p). Othermethods for determining point C(p) are also possible.

Once the complete 3D description of interaction structure 72 has beenestablished (given the available data and assumptions), program flowcontinues to 110 b. At 110 b, a method M is constructed that maps pointsof interaction structure 72 to computer screen interaction region 51.Such methods are well known to those skilled in the art. For example, amethod such as that described in U.S. Pat. No. 6,373,961 to Richardsonet al. (2002) may be used, but other appropriate methods may also beused. For completeness, the method disclosed in the Richardson et al.'961 patent will briefly be explained here. Referring to FIG. 20,interaction structure 72 may be defined by line segments JK and ML.Furthermore, point F may define point-of-aim 210, which is also theintersection between the z′-axis and interaction structure 72. The linesegments JK and ML are generally not parallel. If not parallel, then theline segments JK, ML are extended until they meet at a point H. Then aline is drawn through F and H, that intersects segment. JM at point Pand segment KL at point O. If the segments JK and ML are parallel, the aline is drawn instead through F that is parallel to JK, and whichintersects the other two line segments as described. The processcontinues similarly with the other segments, which are extended to meetat point G. A line through F and G intersects segment JK at point R andsegment ML at point Q. Subsequently, the following distances aremeasured and noted as percentages: JR/JK, KO/KL, LQ/LM and MP/MJ. Thenfour points S, T, U, V are chosen as shown in FIG. 20, that form anexact rectangle STUV; this rectangle may define computer screeninteraction region 51. Further, points W, X, Y, Z are chosen on thesides of the rectangle STUV in such a way that SZ/ST=JR/JK, TW/TU=KO/KL,UX/UV=LQ/LM and VY/VS=MP/MJ. Then the points Z and X are joined by aline, and the points Y and W are joined by a line. The point of theintersection of these latter two lines is N, which is the point thatresults from the operation of method M.

Referring once again to FIG. 6, after 110 b, program flow continues to110 c where a decision is made whether the user has requested theprogram to end. If the decision is positive, the program ends at 110 k.

If the decision at 110 c is negative, program flow continues to 110 d,where a decision is made regarding whether the user has requested adirect-pointing action, such as activating button 203 a or 203 b or thelike.

If the decision at 110 d is negative, program flow continues to 110 e,where the light-beam projection device 202 can be instructed or causedto de-activate (using, for example, control device 204 and/or 304).Furthermore, a software routine (not shown) that controls computercursor 501 (see also FIG. 2) is instructed that the user does not wantto execute a direct-pointing action, after which program flow reverts to110 c. Such cursor control routines are well known to those skilled inthe art and are therefore not described here.

If the decision at 110 d is positive, program flow continues to 110 f,where a decision is made whether the z′-axis intersects interactionstructure 72. Those skilled in the art will appreciate that this ispossible because all relevant 3D information is known or is measurableby coordinate sensing device 201 and 301. If the decision is positive,program flow continues to 110 h, at which method M is used to map theintersection point of the z′-axis with interaction structure 72 tocomputer screen interaction region 51. This mapped position, as well asthe user's desire to execute a direct-pointing action are communicatedto the cursor control routine (not shown) running on the computer.

After 110 h, program flow continues to 110 i where a decision is madewhether the user wishes to execute an action associated with theposition of cursor 501. For example, activating button 203 a or 203 b orthe like may indicate such a request. If the decision is negative,program flow reverts to 110 c.

If the decision at 110 i is positive, program flow continues to 110 j,where the cursor control routine (not shown) is requested to execute theintended action. Such an action may, for instance, be a ‘double-click’action or the like. Program flow then reverts to 110 c.

There may be situations for which the system of equations that allowsdetermination of all coordinates of the points in set P will be somewhatill-posed. This could for example occur if locations CA and CB arechosen too close together, or if the angles of some pointing lines 21with respect to interaction region 71 are too small, as will beappreciated by those skilled in the art. In such cases, the user may bedirected to choose a different point for locations CA and/or CB fromwhere the various points C(p) are to be highlighted.

Thus, methods and means are disclosed that afford a highly flexible andeasily deployable system for interacting with a presentation in adirect-pointing manner at a location not specifically designed oradapted for such a purpose. Moreover, although it is desirable to havehighly accurate coordinate sensing device 201 and 301, in some instancessuch may not be necessary because the visual feedback afforded by adisplayed cursor will compensate to a large extent for any errors madein the measurements of coordinate parameters. The same holds true forthe importance of any discrepancies between the actual shape ofinteraction region 71 and that of the interaction structure 72 that isassumed to coincide with it. Also, minor discrepancies between theactual position and orientation of interaction region 71 and the assumedposition and orientation of interaction structure 72 (which is assumedto coincide with interaction region 71) need not be of criticalimportance, as will be appreciated by those skilled in the art.

Mathematically, there are infinite possible shapes for interactionstructure 72 as well as infinite a priori relationships, sets P, A, Band methods M. To further explain the invention, what follows is a listof examples that are believed will be encountered most often. Theseexamples are not meant to restrict the scope of the present invention inany way, but merely serve as further clarification.

Referring to FIG. 7, it can be assumed that the venue where thepresentation is to be made is set up such that projection image 70 andinteraction region 71 are substantially rectangular. Such may be thecase when the optical axis of projection device 40 is substantiallyparallel to the normal to projection region 60. Projection region 60 maybe a projection screen on a stand, as shown, but may also be a wall orany other substantially vertical surface. It can also be assumed thatthe bottom and top edges of both projection image 70 and interactionregion 71 are substantially horizontal. Furthermore, it can be assumedthat interaction region 71 is substantially the same size as projectionimage 70 and that computer screen interaction region 51 is substantiallythe same size as computer screen image 50. Additionally, it can beassumed that calibration points 721 a, 721 d substantially coincide withthe projected versions of screen marks 521 a, 521 d. Finally, it isassumed that base station 30 is positioned such that the x-y-plane issubstantially horizontal and the x-z-plane substantially coincides withthe plane of interaction region 71. To facilitate in the positioning ofbase station 30, the user may be aided by level-sensing device 303 andvisible markings 302.

Referring to FIGS. 3 and 7, process elements 80 a-j may then result,either through default settings or through user-supplied settings, inthe assumptions that interaction structure 72 is a rectangle that liesin the x-z plane and that its top and bottom edges are parallel to thex-y plane.

Referring to FIGS. 4 and 7, program element 90 a may then result in aset P containing three points that define the upper-right corner C(1),the upper-left corner C(2) and the lower-left corner C(3) of interactionstructure 72. Additionally, program element 90 a may determine point CA(not denoted as such in FIG. 7) to lie away from projection region 60,for example at the center of one of the two instantiations of pointingdevice 20, as shown in FIG. 7. Point CB may be determined anywhere inspace. Program element 90 a may also result in sets A and B eachcontaining three lines, connecting the points in set P to points CA andCB respectively. Program element 90 c may then result in a priorirelationships such that all points in set P have y-coordinate equal tozero, that the upper-left corner will have an x-coordinate equal to thex-coordinate of the lower-left corner and that its z-coordinate will beequal to the z-coordinate of the upper-right corner. It will then beappreciated by those skilled in the art that this a priori information,together with complete 3D information on two lines in set A will besufficient to uniquely determine the position, size and orientation ofinteraction structure 72 with respect to the x y z coordinate system.Therefore, program elements 90 d, 90 e, 90 f, 90 g may result in anempty set B. Moreover, program elements 90 h, 90 i, 90 j, 90 k mayresult in the removal from set A of line A(2), connecting point CA topoint C(2).

Referring to FIGS. 5 and 7, program elements 100 a-p may result in theprogram identifying point C(1) by instructing the computer (not shown)and projection device 40 to project screen mark 521 a onto projectionregion 60, resulting in the appearance of calibration point 721 a.Subsequently, the user is required to use light-beam projection device202 to highlight calibration point 721 a and indicate the success ofthis action to the computer (not shown) by, for example, pressing button203 a. As a result, the orientation and position of the z′-axis areassumed to define line A(1). The same actions are then performed forpoint C(3) and line A(3). Since set B is empty, the user need not berequired to reposition pointing device 20. The two depictions ofpointing device 20 in FIG. 7 are meant to illustrate that pointingdevice 20 only needs to be redirected and not repositioned during thisexercise. It will be appreciated by those skilled in the art thatprogram element 100 p will then successfully result in a full 3Ddescription of the three points in set P.

Referring to FIGS. 6 and 7, program element 110 a may then result in thedescription of interaction structure 72 as a rectangle with upper-rightcorner C(1), upper-left corner C(2) and lower-left corner C(3). Step 110b may then result in a method M that maps a point δ (not shown) ininteraction structure 72 to a point ε (not shown) in computer screeninteraction region 51 in such a way that the ratio of distances betweenδ and any two of the four corners of interaction structure 72 is thesame as the ratio of distances between ε and the two correspondingcorners of computer screen interaction region 51, as will be appreciatedby those skilled in the art. Steps 110 c-k may then result in a veryintuitive cursor control device that responds to a direct-pointingaction by de-activating light-beam projection device 202 and showingcursor 501 at substantially point-of-aim 210 of pointing device 20whenever point-of-aim 210 lies in projection image 70 (which in thisexample, by assumption, substantially coincides with interaction region71). Since there is no necessity for a computer generated cursor and alight spot to be visible simultaneously there will not be any cause forconfusion as to which of the two is the ‘actual cursor’. Cursor 501 maybe hidden from view when point-of-aim 210 does not lie in interactionstructure 72, in which case light-beam projection device 202 may beactivated automatically. Also, intuitive actions such as ‘double click’may be provided by steps 110 c-k.

Referring to FIG. 8, it can be assumed that the venue where thepresentation is to be given is set up such that projection image 70 andinteraction region 71 are substantially rectangular. Such may be thecase when the optical axis of projection device 40 is substantiallyparallel to the normal to projection region 60. Projection region 60 maybe a projection screen on a stand, as shown, but may also be a wall orany similar surface. Projection region 60 can be assumed to be orientedsubstantially vertically. It can also be assumed that the bottom and topedges of both projection image 70 and interaction region 71 aresubstantially horizontal. Furthermore, it can also be assumed thatinteraction region 71 is substantially the same size as projection image70 and that computer screen interaction region 51 is substantially thesame size as computer screen image 50. Additionally, it can be assumedthat calibration points 721 a, 721 c, 721 d substantially coincide withthe projected versions of screen marks 521 a, 521 c, 521 d. Finally, itcan be assumed that base station 30 is positioned such that thex-y-plane is substantially horizontal. No assumptions are made regardingthe x-z-plane and the y-z-plane other than that they are substantiallyvertical. To facilitate in the positioning of base station 30, the usermay be aided by level-sensing device 303.

Referring to FIGS. 3 and 8, program elements 80 a-j may then result,either through default settings or user-supplied settings, in theassumptions that interaction structure 72 is a rectangle of which thetop and bottom edges are parallel to the x-y-plane (i.e., they arehorizontal) and the left and right edges are perpendicular to thex-y-plane (i.e., they are vertical).

Referring to FIGS. 4 and 8, program element 90 a may then result in aset P containing three points that define the upper-left corner C(1),the upper-right corner C(2) and the lower-left corner C(3) ofinteraction structure 72. Additionally, program element 90 a maydetermine point CA (not denoted as such in FIG. 8) to lie away fromprojection region 60, for example, at the center of one of the threeinstantiations of pointing device 20, as shown in FIG. 8. Point CB (notdenoted as such in FIG. 8) may be determined to be displaced from pointCA in a direction substantially parallel to interaction region 71, overa distance that may be the same order of magnitude as the size ofinteraction region 71. Program element 90 a may also result in sets Aand B each containing three lines, connecting the points in set P topoints CA and CB respectively. Program element 90 c may then result in apriori relationships requiring that the upper-left corner will have x-and y-coordinates equal to the x- and y-coordinates of the lower-leftcorner and that its z-coordinate will be equal to the z-coordinate ofthe upper-right corner. As will be explained in detail below, the apriori information together with complete 3D information on two lines inset A and one line in set B will be enough to uniquely determine theposition, size and orientation of interaction structure 72 with respectto the x y z coordinate system. Therefore, program elements 90 d, 90 e,90 f, 90 g may result in set B containing only line B(3). Moreover,program elements 90 h, 90 i, 90 j, 90 k may result in set A containingonly lines A(1) and A(2)

Referring to FIGS. 5 and 8, program elements 110 a-p may result in theprogram identifying point C(1), C(2) and C(3) by means of projectiondevice 40, in a manner similar to the one described in the previousexample. In this case, however, C(1) and C(2) may be highlighted fromapproximately the same location CA, but C(3) needs to be highlightedfrom a different location CB. To explain that the above-mentionedinformation is enough to uniquely establish the position, size andorientation of interaction structure 72, define the points in set P as:$\begin{matrix}{{C(1)} = \begin{pmatrix}{x_{1} + {\lambda_{1} \cdot {Rx}_{1}}} \\{y_{1} + {\lambda_{1} \cdot {Ry}_{1}}} \\{z_{1} + {\lambda_{1} \cdot {Rz}_{1}}}\end{pmatrix}} & (1) \\{{C(2)} = \begin{pmatrix}{x_{1} + {\lambda_{2} \cdot {Rx}_{2}}} \\{y_{1} + {\lambda_{2} \cdot {Ry}_{2}}} \\{z_{1} + {\lambda_{2} \cdot {Rz}_{2}}}\end{pmatrix}} & (2) \\{{C(3)} = \begin{pmatrix}{x_{3} + {\lambda_{3} \cdot {Rx}_{3}}} \\{y_{3} + {\lambda_{3} \cdot {Ry}_{3}}} \\{z_{3} + {\lambda_{3} \cdot {Rz}_{3}}}\end{pmatrix}} & (3)\end{matrix}$

Here, points CA and CB are defined as (x₁, y₁, z₁) and (x₃, y₃, z₃)respectively. Moreover, lines A(1), A(2) and B(3) are defined as passingthrough CA, CA and CB respectively, lying in directions governed by(Rx₁, Ry₁, Rz_(z)), (Rx₂, Ry₂, Rz₂) and (Rx₃, Ry₃, Rz₃). All of thesequantities are presumed to be measured by coordinate sensing device 201and 301. For a unique description of the points in set P a solution isrequired for λ₁, λ₂ and λ₃.

Using these definitions the conditions described above can be writtenas: $\begin{matrix}{{\begin{bmatrix}{Rz}_{1} & {- {Rz}_{2}} & 0 \\{Rx}_{1} & 0 & {- {Rx}_{3}} \\{Ry}_{1} & 0 & {- {Ry}_{3}}\end{bmatrix}\begin{pmatrix}\lambda_{1} \\\lambda_{2} \\\lambda_{3}\end{pmatrix}} = \begin{pmatrix}0 \\{x_{3} - x_{1}} \\{y_{3} - y_{1}}\end{pmatrix}} & (4)\end{matrix}$

which can be solved in a straightforward manner according to theexpression: $\begin{matrix}{\begin{pmatrix}\lambda_{1} \\\lambda_{2} \\\lambda_{3}\end{pmatrix} = \begin{pmatrix}{\left\lbrack {{{Rx}_{3} \cdot \left( {y_{3} - y_{1}} \right)} + {{Ry}_{3} \cdot \left( {x_{1} - x_{3}} \right)}} \right\rbrack/\left\lbrack {{{Rx}_{3} \cdot {Ry}_{1}} - {{Rx}_{1} \cdot {Ry}_{3}}} \right\rbrack} \\{\left\lbrack {{Rz}_{1}/{Rz}_{2}} \right\rbrack \cdot {\left\lbrack {{{Rx}_{3} \cdot \left( {y_{3} - y_{1}} \right)} + {{Ry}_{3} \cdot \left( {x_{1} - x_{3}} \right)}} \right\rbrack/}} \\\left\lbrack {{{Rx}_{3} \cdot {Ry}_{1}} - {{Rx}_{1} \cdot {Ry}_{3}}} \right\rbrack \\{\left\lbrack {{{Rx}_{1} \cdot \left( {y_{3} - y_{1}} \right)} + {{Ry}_{1} \cdot \left( {x_{1} - x_{3}} \right)}} \right\rbrack/\left\lbrack {{{Rx}_{3} \cdot {Ry}_{1}} - {{Rx}_{1} \cdot {Ry}_{3}}} \right\rbrack}\end{pmatrix}} & (5)\end{matrix}$

Note that this solution shows that, if point C(3) was highlighted fromany point on pointing line 21 that is used to highlight point C(1),i.e., $\begin{matrix}{\begin{pmatrix}x_{3} \\y_{3} \\z_{3}\end{pmatrix} = \begin{pmatrix}{x_{1} + {\tau \cdot {Rx}_{1}}} \\{y_{1} + {\tau \cdot {Ry}_{1}}} \\{z_{1} + {\tau \cdot {Rz}_{1}}}\end{pmatrix}} & (6)\end{matrix}$

the solution for the three unknown λ's would collapse to $\begin{matrix}{\begin{pmatrix}\lambda_{1} \\\lambda_{2} \\\lambda_{3}\end{pmatrix} = \begin{pmatrix}\tau \\{\tau\quad{{Rz}_{1}/{Rz}_{2}}} \\0\end{pmatrix}} & (7)\end{matrix}$

making unique determination of interaction structure 72 impossible.Conversely, the fact that points C(1) and C(2) are, in this example,both highlighted from substantially the same point CA does not cause anyproblems. It will be appreciated by those skilled in the art that C(1)and C(2) may also be highlighted from different points, without loss offunctionality.

Referring to FIGS. 6 and 8, the course and results of program elements110 a-k will be similar to those described in Example 1.

Referring to FIG. 9, in another example, the only assumptions made arethat interaction region 71 is substantially the same size as projectionimage 70, computer screen interaction region 51 is substantially thesame size as computer screen image 50, calibration points 721 a, 721 b,721 c, 721 d substantially coincide with the projected versions ofscreen marks 521 a, 521 b, 521 c and 521 d and computer screeninteraction region 51 is substantially rectangular. This situation mayarise when the optical axis of projection device 40 is not aligned withthe normal to projection surface 60.

Referring to FIGS. 3 and 9, program elements 80 a-j may then result,either through default settings or user supplied settings, in theassumption that interaction structure 72 is a quadrangle; no assumptionsare made regarding its position or orientation.

Referring to FIGS. 4 and 9, program elements 90 a may then result in aset P containing four points that define the upper-right, upper-left,lower-right and lower-left corners of interaction structure 72.Additionally, program element 90 a may conceive point CA (not denoted assuch in FIG. 9) to lie away from projection region 60, for example atthe center of the first of the two instantiations of pointing device 20,as shown in FIG. 9. Point CB may, for example, be determined to lie atthe center of the second of the two instantiations of pointing device20, as drawn in FIG. 9. Now, program elements 90 d, 90 e, 90 f, 90 g andsteps 90 h, 90 i′, 90 j, 90 k may result in sets A and B each containing4 lines.

Referring to FIGS. 5 and 9, program elements 110 a-p may result in theprogram identifying the four points in set P by means of projectiondevice 40, in a manner similar to the one described in Example 1. Inthis case, however, all four points in set P may be highlighted fromapproximately the same location CA first, after which all four pointsmay be highlighted from approximately the same location CB. Note thatFIG. 9, for reasons of clarity, only depicts the highlighting ofcalibration point 721 a. Each point C(i) may then be constructed as thepoint lying halfway the shortest line segment connecting lines A(i) andB(i); this line segment may have zero length.

Referring to FIGS. 6 and 9, the course and results of program elements110 a-k will be similar to those described with respect to the firstexample, with the exception of program element 110 b, the mappingelement. Now, a more elaborate method M is needed than the one describedin previous examples. For example, a method such as described in U.S.Pat. No. 6,373,961 to Richardson (2002) may be utilized, but otherappropriate methods may also be used.

A second embodiment will now be made with reference to FIG. 10, whichshows pointing device 20 and base station 30. Here, in addition to anyor all of the elements mentioned in the previous embodiment, pointingdevice 20 is also provided with distance measuring device 206, theposition and orientation of which with respect to the x′ y′ z′coordinate system may be ascertained at the place of manufacture thereofand will be presumed to be known. Distance measuring device 206 may forexample be embodied by a focus adjustment, or optical sensor. A digitalcamera may also be used. Distance measuring device 206 may determine thepoint-of-aim-distance 211 between the origin of the x′ y′ z′ coordinatesystem and the point-of-aim, measured substantially parallel to thez′-axis (see also FIG. 2). The point of aim 210 may lie on projectionregion 60, on which interaction region 71 may lie. Distance measuringdevice 206 may have associated with it a manual focus adjustment thatmay be adjusted by the user (manual focus adjustment not shown).Alternatively, distance measuring device 206 may comprise a circuit (notshown) that automatically determines the point-of-aim-distance 211between the origin of the x′ y′ z′ coordinate system and thepoint-of-aim. For example, if the point-of-aim lies on projection region60, distance measuring device 206 may bounce light off of projectionregion 60. In doing so, use may for instance be made of light-beamprojection device 202. Any other appropriate mechanism for determiningdistance may also be used for distance measuring device 206. The opticalaxes of light-beam projection device 202 and distance measuring device206 may coincide, for instance by making use of partially-reflectingelements (not shown) such as disclosed in U.S. Pat. No. 4,768,028 toBlackie (1988).

The operation of the present embodiment will now be described withreference to FIGS. 2, 10, and 3. The process elements in FIG. 3 will beidentical to the ones described in the first embodiment, resulting insimilar assumptions regarding the shape of interaction region 71 (andinteraction structure 72) and possibly orientation and position ofinteraction structure 72.

Referring to FIG. 11, instead of the program elements described abovewith reference to FIG. 4, program flow now continues at 120 a. Programelements 120 a-120 h are shown to be similar to program elements 90 a-90m (FIG. 4), except that only point CA, set A and counter a areconsidered. That is to say, in the present embodiment it is no longernecessary to determine the second point CB and associated repositioningof pointing device 20 during the calibration procedure.

After program element 120 h, program flow continues with programelements outlined in FIG. 12. Referring to FIG. 12, program elements 130a-130 g are seen to be similar to steps 110 a-110 p (FIG. 5). Comparingprogram element 130 f with program element 110 f (FIG. 5), it can beseen that at 130 f the program also stores information on thepoint-of-aim-distance (211 in FIG. 2) between the origin of the x′ y′ z′coordinate system and point C(p). Comparing elements 130 g and 100 p(FIG. 5), it can seen that these point-of-aim-distances (211 in FIG. 2)are also used in determining the 3D coordinates of the points in set P.

With complete information on the 3D coordinates of the points in set P,it is then possible to construct a 3D description of interactionstructure 72 (in FIG. 2). Therefore, program elements 110 a-110 k asdescribed above with reference to FIG. 6 may also be followed in thepresent embodiment.

Thus, methods and means are disclosed that afford a highly flexible andeasily deployable system for interacting with a presentation in adirect-pointing manner at a location not specifically equipped for sucha purpose. Moreover, when utilizing the second preferred embodiment itis often sufficient for the user to highlight various calibration points721 a, 721 b, . . . from one and the same position, making thecalibration procedure even more easy to follow.

Another embodiment will now be explained with reference to FIG. 13. FIG.13 shows another embodiment of the pointing device 20. Pointing device20 may be equipped with any or all of the elements mentioned in theother embodiments, such as described above with reference to FIG. 1 andFIG. 10. The present embodiment may include a base station 30 that hasassociated with it a coordinate system x y z. However, in the presentembodiment it can be assumed that the position of pointing device 20will remain substantially unchanged relative to interaction region 71over an extended period of time, and that the origin of coordinatesystem x y z may be assumed to be virtually anywhere instead of beingrelated to the base station 30. Furthermore, if any of the axes of the xy z system are chosen to be related to (locally) well-established,independent and stationary directions such as, for example, the Earth'smagnetic field and/or the Earth's gravitational field, the Earth itselfmay be interpreted as embodying base station 30. Under suchcircumstances there may not be a need for an artificial base station 30;coordinate sensing device 201 may then, for example, be embodied bydevices sensing the directions of the Earth magnetic and gravitationalfields, such as accelerometers and a compass (for example, model no.HMR3300 device as manufactured by Honeywell International Inc.,Morristown, N.J.), and communication and control device 204 may beconfigured to communicate directly with the computer (not shown).

The operation of the present embodiment will now be described withreference to FIGS. 8, 13, and 3. The remainder of the description of thepresent embodiment will, for purposes of explanation, include theassumption that any separately embodied base station 30 (FIGS. 8 and 13)is omitted entirely. It is also assumed that one of the axes of theorthogonal coordinate system x z is substantially parallel to theEarth's gravity field (or has a defined relationship thereto), while thesecond and third axes of the coordinate system are in a fixed, knownrelationship to the at least one geographically defined axis. In thepresent embodiment it is assumed that the relative position of pointingdevice 20 with respect to interaction region 71 remains substantiallyunchanged, therefore the origin of coordinate system x y z will, forpurposes of explanation, be chosen to coincide with a fixed point in thepointing device 20. For the purpose of the present embodiment, it shouldbe understood that the three instantiations of pointing device 20 asshown in FIG. 8 substantially coincide.

It can be assumed in the present embodiment that a display system isarranged at the venue where a presentation is to be made, as acombination of a portable projection device 40 and projection surface60, for example a wall. It will furthermore be assumed that this displaysystem is connected, using appropriate means, to the computer (notshown) that generates the

Upon arriving at the venue, the user connects pointing device 20 to thecomputer (not shown), for example via a USB connection (not shown), orusing a wireless relay device (not shown). Also, the computer mayrecognize the connection and start a program, part of which may becontained in communication and control device 204 or in control logiccontained in the wireless relay device itself (not shown).Alternatively, the user may be required to load the program into thecomputer manually via a CD drive, a floppy drive, memory stick or thelike (not shown). In any case, the program may initiate a calibrationroutine that has as its object establishing the shape, position, sizeand orientation of a well-defined interaction structure 72, relative tothe x y z coordinate system, wherein the interaction structure 72 isassumed to substantially coincide with a scaled and parallel version ofinteraction region 71. The flow of this program will be explained withreference to FIG. 3.

At 80 a the program is initiated. At 80 b defaults are entered forinteraction region 71. Specifically, interaction region 71 is assumed tobe a substantially parallel and scaled version of a well-definedinteraction structure 72. Moreover, the respective corners ofinteraction region 71 and interaction structure 72 are assumed tosubstantially lie on lines intersecting each other in the origin ofcoordinate system x y z. It should be noted that FIG. 8 shows aninteraction region 71 and an interaction structure 72 that are almostcoincident, but this is only meant for illustrative purposes and is nota limitation on the scope of the invention. Again referring to FIG. 3,at 80 b default values are also established for the orientation andposition of the interaction structure 72. For example, the defaultvalues may provide that interaction region 71 is substantially aparallel and scaled version of an interaction structure 72 that is aflat rectangle of which the two most vertical sides are substantiallyparallel to the Earth's gravitational field, and of which the two mosthorizontal sides are substantially perpendicular to the Earth'sgravitational field; moreover, the default values may provide that therespective corners of interaction region 71 and interaction structure 72substantially lie on lines intersecting each other in the origin ofcoordinate system x y z. The default values may furthermore provide thatthe position of interaction structure 72 is such that the distancebetween pointing device 20 and the lower left corner of interactionstructure 72 is equal to 1. Note that other values for the foregoingdistance may be equally valid in the present embodiment. Based on theforegoing default values, calibration points 721 a, 721 c, 721 d, . . .can define characteristic features of interaction region 71 and can alsodefine characteristic features of interaction structure 72.

At 80 c a decision is made whether the default values for interactionregion 71 and interaction structure 72 should be accepted or overriddenby the user. If the default values are to be accepted, the program flowcontinues to 80 j, the details of which are explained below withreference to FIG. 11. If the defaults are to be overridden, the programflow continues with elements 80 d-80 i, during which the user mayoverride any of the default settings. The user may be aided duringprogram elements 80 d-80 i by a library of predetermined shapes,predetermined orientations and/or predetermined positions.Alternatively, the user can be provided with the capability to constructcustom shapes, orientations and/or positions. In any event, program flowcontinues to 80 j.

Referring to FIG. 11, program flow now continues to 120 a. Programelements 120 a-120 h are substantially similar to program elements 90a-90 m (FIG. 4), except that only point CA, set A and counter a areconsidered. In the present embodiment it is not required to determine asecond point CB and an associated repositioning of pointing device 20during the calibration procedure.

After 120 h, program flow continues with elements described withreference to FIG. 14. In FIG. 14, program elements 140 a-140 g are shownto be similar to steps 130 a-130 g (FIG. 12). Comparing element 140 fwith element 130 f (FIG. 12), it can be seen that element 140 f does notinclude storing information for any directly measured distance. Element140 f need not include storing information on the position of thez′-axis, because the position of pointing device 20 is assumed to remainsubstantially unchanged over an extended period of time. Comparingelements 140 g and 130 g, it can be seen that any directly measureddistance is not needed to determine the 3D coordinates of the points inset P (see FIG. 4). In fact, having the default distance (set to 1)between pointing device 20 and the lower left corner of interactionstructure 72 is sufficient for operation of the system in the presentembodiment. To explain this fact, reference is again made to FIG. 8.Using the above default values, interaction structure 72 will becompletely defined by, for example, its upper-left corner C(1), itsupper-right corner C(2) and its lower-left corner C(3) $\begin{matrix}{{C(1)} = {\lambda_{1} \cdot \begin{pmatrix}{Rx1} \\{Ry1} \\{Rz1}\end{pmatrix}}} & (8) \\{{C(2)} = {\lambda_{2} \cdot \begin{pmatrix}{Rx2} \\{Ry2} \\{Rz2}\end{pmatrix}}} & (9) \\{{C(3)} = {\lambda_{3} \cdot \begin{pmatrix}{Rx3} \\{Ry3} \\{Rz3}\end{pmatrix}}} & (10)\end{matrix}$

lying on lines A(1), A(2) and A(3) that connect the origin to points(Rx₁, Ry₁, Rz₁), (Rx₂, Ry₂, Rz₂) and (Rx₃, Ry₃, Rz₃) respectively. Usingthese definitions, the conditions described above determinerelationships between the various variables that can be written as$\begin{matrix}{{\begin{bmatrix}{Rz}_{1} & {- {Rz}_{2}} & 0 \\{Rx}_{1} & 0 & {- {Rx}_{3}} \\{Ry}_{1} & 0 & {- {Ry}_{3}}\end{bmatrix}\begin{pmatrix}\lambda_{1} \\\lambda_{2} \\\lambda_{3}\end{pmatrix}} = \begin{pmatrix}0 \\0 \\0\end{pmatrix}} & (12)\end{matrix}$

which will have non-trivial solutions only if the determinant of thematrix equals zero. Then, it can be shown that any combination of (λ₁,λ₂, λ₃) that can be written in the form: $\begin{matrix}{\begin{pmatrix}\lambda_{1} \\\lambda_{2} \\\lambda_{3}\end{pmatrix} = {\begin{pmatrix}{{Rz2}/{Rz1}} \\1 \\{\left( {{Rz2} \cdot {Rx1}} \right)/\left( {{Rz1} \cdot {Rx3}} \right)}\end{pmatrix} \cdot \alpha}} & (13)\end{matrix}$

where α is any arbitrary real number, will generate solutions forinteraction structure 72 that are parallel to each other. The assumptionthat the distance between pointing device 20 and the lower left cornerof interaction structure 72 is 1 will hence uniquely generate one ofthese solutions. To see that other assumptions regarding this distancedo not influence the operation of the present embodiment, reference ismade to FIG. 15. In FIG. 15, projections of two parallel solutions forinteraction structure 72 are shown, obtained for different values ofdistances CA-C(3). When it is assumed, for purposes of explanation, thatthese two solutions are parallel to the z-x plane, FIG. 15 may beinterpreted as a projection of the two solutions onto the x-y plane.These projections are shown as the thick line segments C(3)-C(2) andCC3-CC2. FIG. 15 also shows the projection of point CA (i.e., the originof coordinate system x y z), from where the lower left and upper rightcorners of interaction structure 72 were highlighted, and line-segmentsC(3)-CA and C(2)-CA which coincide with the (projections of) thehighlighting lines A(3) and A(2) (not denoted as such in FIG. 15).Finally, line-segment BB1-CA indicates (the projection of) a pointingline that is consistent with a point-of-aim BB1 on the one andpoint-of-aim BB2 on the other of the two solutions for interactionstructure 72. To show that BB1 and BB2 represent the same horizontalcoordinate when measured relative to the appropriate solution forinteraction structure 72, the lengths of line-segments C(3)-BB1,C(2)-BB1, CC3-BB2, CC2-BB2, BB1-CA and BB2-CA are represented by bb1,bb2, b1, b2, aa12 and a12, respectively. It is sufficient to show thatbb1/bb2=b1/b2. Consider the following equalities: $\begin{matrix}{\frac{bb1}{\sin\quad{\beta 1}} = \frac{aa12}{\sin\quad{\alpha 1}}} & (14) \\{\frac{bb2}{\sin\quad{\beta 2}} = \frac{aa12}{\sin\quad{\alpha 2}}} & (15)\end{matrix}$

while, at the same time $\begin{matrix}{\frac{b1}{\sin\quad{\beta 1}} = \frac{a12}{\sin\quad{\alpha 1}}} & (16) \\{\frac{b2}{\sin\quad{\beta 2}} = \frac{a12}{\sin\quad{\alpha 2}}} & (17)\end{matrix}$

From this it follows that $\begin{matrix}{\frac{aa12}{bb1} = \frac{a12}{b1}} & (18) \\{\frac{aa12}{bb2} = \frac{a12}{b2}} & (19)\end{matrix}$

which, in turn, provides that $\begin{matrix}{{{bb1}\quad\frac{a12}{b1}} = {\left. {{bb2}\quad\frac{a12}{b2}}\Rightarrow\frac{bb1}{bb2} \right. = \frac{b1}{b2}}} & (20)\end{matrix}$

This implies that BB1 and BB2 represent the same horizontal coordinatewhen measured relative to the appropriate solution for interactionstructure 72. Note that, if FIG. 15 is interpreted as a projection ontothe z-y-plane, it can be concluded that BB1 and BB2 also represent thesame vertical coordinate when measured relative to the appropriatesolution of interaction structure 72. Therefore the initial assumptionthat the distance between C(3) and CA is equal to 1 does not influencethe operation of the third preferred embodiment.

It is theoretically possible that there are no non-zero solutions forthe parameters λ₁, λ₂ and λ₃, when the determinant referred to above inequation (12) is non-zero. Such may be the case, for example, due toerrors in measurements or in the assumed rectangular shape ofinteraction region 71. In such cases additional techniques may be usedto find an acceptable solution for interaction structure 72. Forexample, a minimization routine may be used to find a solution forinteraction structure 72 that minimizes a summation of the distancesbetween some of its corners (which, by assumption, lie on linesconnecting the origin of coordinate system x y z with the corners ofinteraction region 71) and the highlighting lines.

With complete information on the 3D coordinates of C(1), C(2) and C(3)it is possible to construct a 3D description of interaction structure72. Therefore, program elements 110 a-110 k as described in the firstembodiment and explained above with reference to FIG. 6 may also befollowed in the present embodiment.

There may be situations in which the user is not able to hold pointingdevice 20 continuously at precisely the same position while performingthe actions required by the calibration procedure described in FIGS. 3,11 and 14, or during the use of the system as a direct-pointing device.Such changes in position of the pointing device 20 can cause errors inthe calculation of the point-of-aim. It will be appreciated that if thediscrepancy between the calculated and the true point-of-aim is smallenough, the visual feedback provided by the displayed cursor (501 inFIG. 1) during use of the system as a direct-pointing device will stillafford the user the perception that direct-pointing is being performed.

There are many other methods capable of establishing position, size andorientation of interaction structure 72, as will be appreciated by thoseskilled in the art. For example, if the distance between pointing device20 and interaction structure 72 is presumed known, if interactionstructure 72 is assumed to be rectangular with two vertical and twohorizontal sides and if its aspect ratio (the ratio between itshorizontal size and its vertical size) is also presumed known, thenknowledge of two lines from CA to the upper-right and lower-left corneris sufficient to narrow the number of solutions for interactionstructure 72 down to 2, dictated by 2 solutions of a quadratic equation.One further assumption is then required to determine which of these 2solutions is the correct one; this assumption may be in the form of athird line passing through yet another characteristic point ofinteraction structure 72, but it may also be in the form of knowledge ofthe (approximate) angle between the plane in which interaction structure72 lies and a line connecting the origin to one of its corners. Otherscenarios may also be conceived for which solutions may be devised thatare within the scope of the general methods set forth herein.

In the present embodiment, using well-established and stationarydirections such as, for example, the Earth's magnetic field and theEarth's gravitational field, it may be possible to omit a separatelyembodied base station, making the present embodiment of the systempossibly more compact, less expensive to make and easier to deploy.

Another embodiment of a system according to the invention will now bedescribed with reference to FIG. 16. In the present embodiment ahandheld presentation device 25 contains a power source 205,communication and control device 204 and a directional sound recordingdevice 251. The sensitivity region of the directional sound recordingdevice 251 may be substantially oriented along the long axis ofpresentation device 25. Any or all of the features contained in pointingdevice 20, already described in previous embodiments or to-be-describedin the additional embodiments, may also be contained in presentationdevice 25; any or all of features 201-207 are collectively depicted asmodule 200. In the same way, the fourth preferred embodiment also maybut need not provide base station 30 and its associated elements, suchas elements 301-305 or a wireless relay device (not shown in FIG. 16).

The directional sound recording device 251 may be provided withso-called zoom capabilities, such as those afforded by, for example, theECM-Z60 Super Zoom Microphone as manufactured by Sony. Alternatively,directional sound recording device 251 may comprise multiple directionalmicrophones (not shown) with different sensitivity regions, so that zoomcapabilities may be emulated. In these cases, presentation device 25 mayalso be provided with zoom control device 252, capable of adjusting thesensitive volume of directional sound recording device 251 either bymanual control or automatically. Directional sound recording device 251may communicate with the computer (not shown) and/or base station 30(not shown in FIG. 16) through communication and control device 204and/or 304 (not shown in FIG. 16). A control program described in FIG.17 may be transferred to the computer (not shown) or be incorporated incommunication and control device 204 and/or 304. Moreover, there may beprovided a storage medium for storage of sound data (not shown) in oneof the components of the described system, as well as means to play backsound, such as a loudspeaker (not shown).

During a presentation it may occur that a member of the audience wishesto communicate verbally with the presenter (user). Often, the acousticsof the room preclude other members of the audience from hearing suchcommunication In such cases, the user may point presentation device 25in the direction of the member of the audience who wishes to communicatewith the user. The user may then activate directional sound recordingdevice 251 by activating controls such as button 203 a or zoom controldevice 252. The latter may also be used to acoustically zoom in on theparticular member of the audience. Directional sound recording device251 may then communicate with the computer (not shown) and record thecommunication, for example, in computer memory (not shown). At the sameor later time the user may request the recording to be played back, forinstance over speakers (not shown) driven by the computer (not shown),by activating controls such as button 203 b. The computer program may beconfigured such that one and the same command from the user, such as theactivation of button 203 a or zoom control device 252, initiatessubstantially simultaneous recording and playback. Measures tocounteract any acoustical interference when playback and recording occuralmost simultaneously may be implemented as well. Such measures are wellknown in the art.

Referring to FIG. 17, to facilitate the recording and playback ofsounds, general elements, 150 a-150 q of a program are shown. Theseprogram elements may be executed by the computer (not shown), and may beloaded into the computer by such means as floppy discs, memory sticks orCDs (not shown). The programs may be pre-loaded in base station 30, itsassociated wireless relay device (both not shown in FIG. 16) orpresentation device 25, and transferred by means of a USB port or thelike (not shown) upon connecting any of these components to the computer(not shown).

At 150 a the program is initialized, old recordings are erased and arecord-flag and a playback-flag are unset; this indicates that bothrecording and playback are not activated.

Program flow continues to 150 b, where a decision is made whether theuser requests the program to end. Buttons (203 a, 203 b in FIG. 16) orthe like may be used for this purpose.

If the decision at 150 b is positive, program flow continues to 150 q,where any recording or playback is stopped, playback and record flagsare unset, old recordings are erased and the program ends. If thedecision at 150 b is positive, program flow continues to 150 c.

At 150 c a decision is made whether the user has requested soundrecording. If the decision is positive, program flow continues to 150 d.If the, decision is negative, program flow continues on to 150 f.

At 150 d a decision is made whether the record-flag is unset, indicatingthat recording is not already in progress. If the decision is negative,program flow continues to 150 f. If the decision is positive, programflow continues to 150 e, where the record flag is set, any oldrecordings are erased and sound recording is started, after which theprogram flow continues to 150 f.

At 150 f, a decision is made whether the user has requested soundplayback. If this decision is positive, program flow continues to 150 g.If the decision is negative, program flow continues to 150 i.

At 150 g a decision is made regarding whether the playback flag isunset, indicating that playback is not already in progress. If thedecision is negative, program flow continues to 150 i. If the decisionis positive, and there is some sound data to be played back, programflow continues to 150 h, where the playback flag is set and soundplayback is started, after which the program flow continues to 150 i.

At 150 i a decision is made whether the user has requested that soundrecording is to be terminated. If the decision is positive, program flowcontinues to 150 j. If the decision is negative, program flow continueson to step 150 m.

At 150 j a decision is made whether the record-flag has been set,indicating that recording is in progress. If the decision is negative,program flow continues to 150 m. If the decision is positive, programflow continues to 150 k, where the record flag is unset and soundrecording is stopped, after which the program flow continues to 150 m.

At 150 m a decision is made whether the user has requested that soundplayback is to be terminated. If the decision is positive, or if the endof the recorded sound has been reached, program flow continues to 150 n.If the decision is negative, program flow reverts to step 150 b.

At 150 n a decision is made whether the playback flag has been set,indicating that playback is in progress. If the decision is negative,program flow reverts to 150 b. If the decision is positive, program flowcontinues to 150 p, where the playback flag is unset and sound playbackis stopped, after which the program flow reverts to 150 b.

Thus, methods and means are disclosed that afford a user the capabilityto easily capture and playback comments made by a member of theaudience, even in the presence of substantial background noise.

While the above description contains many specificities, these shouldnot be construed as limitations on the scope of the invention, Manyother variations are possible. For example, presentation device 25 orpointing device 20 may be hand held, but may also be carried by the userin a different manner, such as by means of a headset, finger-worn ringor the like.

Although the first, second and third embodiments make use of theassumption that the interaction structure 72 and interaction region 71are quadrangles, this need not be the case even when the correspondingcomputer screen interaction region 51 is rectangular in shape. Forexample, projection region 60 may be spherical in shape. This may causethe projection of a square computer screen interaction region 51 toresult in interaction region 71 having the general shape of asphere-segment. Other shapes are also possible, depending on a number offactors such as the angle between the optical axis of projection device40 and projection region 60. It will be appreciated by those skilled inthe art that set P (see FIG. 4, step 90 a and FIG. 11, step 120 a) andmethod M (see FIG. 6, step 110 b) may become more complicated underthese circumstances, but may still be well defined. In fact, method Mand sets P, A, B may be constructed in any way that is advantageous tothe particular system application. It is also possible to determine morepoints and associated line sets than just CA and CB, and associated linesets A and B. Specifically, set P may have more or fewer than the numberof points described with reference to the foregoing embodiments,depending on the complexity of the presentation venue. Also, sets A andB may contain more lines than the minimum number needed to establish thecoordinates of the points in set P.

The present invention may make use of mathematical techniques notdescribed explicitly herein but well known to those skilled in the artto aid with various aspects of the present invention, for example in thedetermination of position and/or orientation of interaction structure72. The second example of the first embodiment, for example, wasdescribed as relying on three lines highlighting corners of theinteraction structure 72. It is also possible that a more accuratesolution for the position and/or orientation of interaction structure 72may be obtained when the user is requested to also highlight the fourthcorner of the screen. An appropriate minimization routine may then beused to find a solution characterized by, for example, a minimumaccumulated distance between the four corners of interaction structure72 and the closest highlighting line.

Moreover, although set P is described as containing points that areneeded to completely define interaction structure 72, other embodimentsof the invention may use so-called “control points” for quality controlpurposes. Such control points may be used to test the validity of theassumptions made concerning, for example, the shape, the position, sizeand/or orientation of interaction region 71 and, therefore, interactionstructure 72, as well as to test the accuracy of the measurements madeto establish the 3D features of the various lines. As an example,consider the case in which interaction structure 72 is taken to be arectangle for which all data needed to uniquely establish its size,orientation and position with respect to the x y z coordinate system hasbeen ascertained by the program elements described with respect to theforegoing embodiments. Moreover, in this example interaction region 71and, therefore, interaction structure 72, are assumed to substantiallycoincide with the projection of a rectangular computer screeninteraction region 51. Then, the computer may display a suitable screenmark 521 a, 521 b, . . . at, for example, the center of computer screeninteraction region 51, which may be projected by projection device 40onto projection region 60. It will be appreciated that the processelements described herein may be used to calculate 3D coordinates ofthis projected point, based on the available data regarding shape, size,orientation and position of interaction structure 72. The user may thenbe required to highlight the projected point using light-beam projectiondevice 202 and indicate the success of this action to the computer by,for example, activating button 203 a. If all measurements andhighlighting actions were accurate enough and no false assumptions weremade, the 3D coordinates of the projected point should substantiallyconform to the 3D characteristics of the z′-axis. If the discrepancy isdeemed too large the user may be required to repeat part or all of thecalibration steps outlined in the present invention.

There may also be more than one method M and sets P, A and B, each ofwhich may be associated with a different interaction structure 72 andinteraction region 71. There may be more than one interaction structure72 and interaction region 71, each of which may, but need not, lie onprojection region 60 and each of which may, but need not, be associatedby means of projecting screen marks 521 a, 521 b, . . . , with one ormore computer screen interaction regions 51.

Although coordinate sensing device (201 and 301 in FIG. 1.) were in someembodiments described as being able to provide information on the 3Dposition and 3D orientation of pointing device (20 in FIG. 2) relativeto the x y z coordinate system, it should be understood that suchinformation provision requirements may be relaxed under somecircumstances. Specifically, in the first embodiment it is only requiredthat the 3D position and 3D orientation of pointing line (21 in FIG. 2)to be known, instead of having complete information on the position ofpointing device (20 in FIG. 2) along the pointing line. That is, in somecases pointing device may be moved along pointing line without loss offunctionality. In such embodiments the coordinate sensing devices needonly provide information on the 3D position and 3D orientation of a line(as opposed to a line-segment) substantially intersecting pointingdevice. If coordinate sensing devices are able to provide complete 3Dinformation (i.e., 3D position and 3D orientation) of pointing device,as opposed to pointing line, the extra positional information may, forexample, be used to implement the capability to zoom in on a regionaround point-of-aim (210 in FIG. 2); other actions may also be based onthe extra positional information. The foregoing capability may beinferred from the description of the third embodiment, in which thecoordinate sensing device only is used to provide information on theangle between the pointing line and two other fixed lines, instead offull position and orientation information about a line segment.

Although the first, second and third embodiments describe theapplication of the invention as a cursor control device, the inventionmay also be used to facilitate non-cursor-related applications. Suchapplications may include “virtual writing” on the interaction region 71,target practice and the like. Also, the invention may be used other thanfor presentations. For example, methods of the invention may be employedto control a cursor on a television screen in order to make selectionsfrom menus associated with such things as Digital Satellite Television;other applications may also be anticipated.

Moreover, the features of the present invention that enable the trackingof point-of-aim relative to an interaction region may be enhanced byalgorithms that allow the filtering of involuntary, fast and/or smallhand-movements (that may be caused, for example, by the activation ofbuttons). Such algorithms may be used to control a point that moves lesserratically than the actual point-of-aim while still being associatedwith it. Such motion filtering may produce a more steady motion ofcursor 501. Such algorithms may also be used when the user is requiredto highlight calibration points 721 a, 721 b, . . . . Filter algorithmsare well-known in the art.

The present invention also contemplates the inclusion into pointingdevice 20 or presentation device 25 of sensors capable of detectingmotion or acceleration, both linear and angular, in addition to or aspart of coordinate sensing device 201. Such sensors may be used todetect unintended motion or acceleration of pointing device 20 orpresentation device 25 that may be caused, for example, by trembling ofthe user's hand. The programs described above with reference to FIGS. 5,6, 12 and 14 may be enhanced by algorithms that compare the output ofsuch sensors and/or coordinate sensing device to predefined thresholds,so that a change in measured orientation and/or position by coordinatesensing device 201 may be recognized as significant only if such outputexceeds these thresholds. Using threshold selection, a change in cursorposition may only be affected if inferred to be intentional, avoidingthe type of “jitter” associated with the use of regular laser pointersby a user with an unsteady hand.

Furthermore, pointing device 20 may be equipped with an image capturingdevice, such as a digital camera, preferably with zoom and controllablefocus capabilities. Other image capturing devices, in combination withappropriate optical devices, may also be used. As stated before, such adigital camera may be used as an embodiment of distance measuring device206. Referring to FIG. 18, such a digital camera or the like (not shown)may also be used to aid in the process of highlighting the calibrationpoints 721 a, 721 b . . . . Images of calibration points 721 a, 721 b, .. . and light spots at point-of-aim 210 may be captured during the timewhen the user is engaged in the highlighting process. These images maybe temporarily stored, together with the position and orientation of thez′-axis at the time the image was acquired. During the highlightingprocess, it is likely that point-of-aim 210 changes slightly. Theresulting sequence of images may then be used to more accuratelyestimate the orientation and position of the pointing line 21 thatconnects the origin of the x′ y′ z′ system to calibration point 721 a,721 b, . . . . For example, an averaging algorithm may be used.Alternatively, the stored position and orientation of the z′-axiscorresponding to the captured image for which the light spot atpoint-of-aim 210 is closest to the center of calibration point 721 a,721 b, . . . may be taken as the position and orientation of thepointing line 21 that connects the origin of the x′ y′ z′ system tocalibration point 721 a, 721 b, . . . .

Some features may also be omitted without affecting the overallapplicability of the present invention. For example, level-sensingdevice (303 in FIG. 1) and visible markings (302 in FIG. 1) may behelpful but are not of critical importance and may be omitted. Iflevel-sensing device 303 are present, the output may also be utilized tocorrect the orientation of the x y z coordinate system to ensure thatits x-y plane is substantially horizontal, as previously explained. Insuch a case, the visible markings 302 may no longer precisely indicatethe position of certain coordinate planes or even the origin of the x yz coordinate system. If the orientation of the uncorrected x-y-planewith respect to a horizontal surface is small enough, though, visiblemarkings 302 may still provide sufficiently reliable information oncoordinate planes and origin of the corrected x y z coordinate system.

Furthermore, the programs outlined in FIGS. 3, 4, 5, 6, 11, 12, 14 and17 may be changed appropriately without loss of functionality,particularly with respect to the order of some of the elements. Theprograms may also be written in any language that is advantageous toparticular the implementation, including without limitation C, Java, andVisualBasic.

Other embodiments that include automatic activation and de-activation oflight-beam projection device 202, or include provision for instructingthe cursor control routines to show or hide computer cursor 501 are alsowithin the scope of the present invention. For example, automaticactivation and de-activation of light-beam projection device 202 mayoccur depending on whether or not the z′-axis intersects one of theinteraction structures 72, or regions of space close to them. This maybe performed by instructions to the cursor control routines to show orhide computer cursor 501. Also, means may be provided to activatelight-beam projection device 202 manually.

Furthermore, pointing device 20 and presentation device 25 may include aconventional, indirect pointing device such as a trackball or the like,to be used in situations where direct pointing is not possible or notdesired. As a practical matter, coordinate sensing device 201, in someembodiments in combination with coordinate sensing device 301, may beused to affect cursor control in an indirect manner if the intended usemakes this desirable. To effect cursor control in indirect pointingapplications, pointing device 20 or presentation device 25 may include auser input device that enables the user to select whether indirectcursor motion control is desired, or may include sensors and/oralgorithms that enable determining when direct pointing actions are notpossible. For example, an algorithm or sensor may be included thatenables determination of whether pointing device 20 or presentationdevice 25 is within the operational range of base station 30. The thirddescribed embodiment, specifically, may be enhanced with algorithmsand/or sensors, such as accelerometers, that enable to determination ofwhether pointing device 20 or presentation device 25 have been displacedsignificantly from the position at which the calibration procedure wasperformed, making direct pointing actions no longer possible withoutadditional calibration steps. As part of the third described embodiment,additional input devices and algorithms may be included that enable theuser to mark an orientation in space such that indirect cursor motioncontrol may be effected based on the changes in orientation with respectto this marked orientation, as described in the cited prior art. Otherembodiments of a system may also be enhanced by such functionality andinput devices.

In addition to the previously described methods to determine size,position and orientation of interaction region 71, other methods arealso within the scope of the invention. These include methods based onthe use of digital cameras and the like. The position and orientation ofsuch cameras, relative to the x y z coordinate system, may be tracked byusing a device such as coordinate sensing device 201 and 301. Forexample, given sufficient knowledge of the optical characteristics of adigital camera, 3D features of an object may be determined from one ormore images taken from one or more positions. Using such images, acomplete 3D description of interaction region 71 may be determined.

Another alternative for establishing 3D position, size and orientationof interaction region 71 is provided by a digital camera or the likeused in addition to, or as embodiment of, the distance measuring device206. In such embodiments the direction relative to the x′ y′ z′coordinate system of the axis along which distance is measured may becontrolled and measured by mounting the digital camera and/or distancemeasuring device 206 in such a way that their orientation relative tothe x′ y′ z′ coordinate system may be controlled and measured. Otherimplementations in which the foregoing components are positionally fixedare also contemplated. For purposes of explanation, the axis along whichdistance is measured is denoted as the z″-axis, and the z″=0 position isassumed to coincide with the origin of the x′ y′ z′ coordinate system.The orientation of the z″-axis with respect to the x′ y′ z′ coordinatesystem, and also with respect to the x y z coordinate system maytherefore be assumed to be known. In this embodiment, calibration points721 a, 721 b, . . . may be displayed simultaneously, as projections ofscreen marks 521 a, 521 b, . . . , and may differ in appearance, suchthat they may be distinguished by image processing software.Alternatively, calibration points 721 a, 721 b, . . . may appear asprojections of screen marks 521 a, 521 b, . . . in an automaticallycontrolled sequence. The user may then be queried to direct pointingdevice 20 in the general direction of interaction region 71 in such away that the digital camera may image the calibration point underconsideration. An automated calibration sequence may then be executed,wherein the z″-axis is directed, in sequence, to calibration points 721a, 721 b, . . . etc. The image processing software may identify thevarious calibration points 721 a, 721 b, . . . and the 3D position ofthese points may then be determined from knowledge of the orientation ofthe z″-axis and the coordinates of the z″=0 position with respect to thex y z coordinate system, in addition to the measuredpoint-of-aim-distance 211 between the calibration points 721 a, 721 b, .. . and the origin of the x′ y′ z′ coordinate system. This embodimentmay also provide light-beam projection device 202 mounted in a way thatenables control of the direction of the light-beam relative to the x′ y′z′ coordinate system. This light-beam may be used to aid in positioningthe z″-axis. Embodiments where light-beam projection device 202 arefixed or left out entirely are also contemplated.

The present invention also contemplates situations in which parts of thecalibration procedures outlined may be repeated at appropriate times.For example, when the relative position of base station 30 andinteraction region 71 changes substantially there may be a need torecalibrate the system. Such may also be the case when the position withrespect to interaction region 72 of pointing device 20 or presentationdevice 25 changes significantly, while operation of a particularembodiment of the invention operated using the assumption that suchposition remains substantially unchanged. As another example, coordinatesensing device 201 and/or coordinate sensing device 301 may includetime-integrated acceleration measuring devices. In such a case accuracyof coordinate sensing may deteriorate over time, because of drift in thebase acceleration measurements. When the deterioration has become largeenough to be unacceptable to the user, the user may be queried to placepointing device 20 in certain defined positions with respect to the x yz coordinate system, so as to re-initialize coordinate sensing device201 and 301.

The present invention also contemplates the use of a plurality ofpointing devices 20 and/or presentation devices 25. Each of theplurality of pointing devices 20 or presentation devices 25 may beuniquely identifiable by the computer, for example by carrying a uniqueID code inside their respective communication and control device 204.Each of the plurality of pointing or presentation devices may beassociated with a specific cursor and/or a specific interaction region71. For example, a first pointing device may be used to control acorresponding cursor on the left-hand one of two interaction regions 71,and a second pointing device may be used to control a correspondingcursor on the right-hand one of two interaction regions 71.Alternatively, both pointing devices may be used to control acorresponding, identifiable cursor on the same interaction region 71.

Furthermore, the present invention contemplates the use of a pluralityof entities such as base station 30, a particular one of which may beassociated with the origin of the x y z coordinate system. Such a basestation may be designated as the ‘master base station’. Each of the basestations may include coordinate sensing device 201, so that theirrespective position and orientation relative to the master base stationcan be determined with greater accuracy than that afforded by thecoordinate sensing device 201 that is incorporated in pointing device20. Using such multiple base stations and coordinate sensing devices, 3Ddata pertaining to pointing device 20 may be determined relative to theclosest base station, and the relative position and orientation of thatbase station with respect to the master base station may be used toestablish the 3D data pertaining to pointing device 20 with respect tothe x y z coordinate system. Alternatively, signals from multiple basestations, as measured by the coordinate sensing device 201 disposed inpointing device 20, may be used simultaneously to reduce measurementerrors. Generally speaking, determining the 3D data pertaining topointing device 20 with respect to the x y z coordinate system by makinguse of only one base station 30 may be less accurate than by making useof a plurality of base stations. Hence, the effective range of operationof pointing device 20 may be enhanced by distributing a plurality ofbase stations over a large region of space.

Referring to FIG. 19, in another embodiment, different devices thanlight-beam projection devices may be used to determine the position ofthe points in set P. For example, light-beam projection device 202 maybe omitted in an embodiment where pointing device 20 has the generalshape of an elongated body, such as a pointing stick. The length of thisstick may be predetermined or variable. For example, pointing device 20could be in the shape of an extendable, or telescopic pen such as theINFINITER Laser Baton sold by Bluesky Marketing—Unit 29, Six HarmonyRow, Glasgow, G51 3BA, United Kingdom. The process of highlighting acalibration point 721 a 721 b, . . . , in this embodiment may bereplaced by the action of pointing to the calibration point 721 a, 721b, . . . , thereby guided by the elongated shape of pointing device 20instead of the light spot shown in FIG. 18 at point-of-aim 210. Distancemeasuring device 206 may also be provided in a related embodiment,similar to the second described embodiment. For example, distancemeasuring device 206 may include a device to measure the distance fromthe tip of the elongated body of pointing device 20 to the origin of thex′ y′ z′ coordinate system. In such an embodiment, in order to obtainmeasurements of point-of-aim-distance 211, as described for example atprogram element 130 f (see FIG. 12), the user might be queried to makephysical contact between the tip of pointing device 20 and thecalibration point. Referring to FIG. 19, pointing device 20 may alsocomprise contact-sensing device 207, for example at the tip of pointingdevice 20, capable of indicating physical contact between the tip ofpointing device 20 and a surface. Contact-sensing device 207 may be inthe form of a pressure-sensor or switch. Such sensors are known in theart.

The present invention also contemplates the use of various other sensorsintegrated in pointing device 20, presentation device 25 and/or basestation 30 to help determine the position and/or orientation ofinteraction structure 72. For example, pointing device 20, presentationdevice 25 and/or base station 30 may include ultrasonic emitting anddetecting devices to enable measuring substantially the shortestdistance between a known point in the x y z coordinate system (e.g., theposition of pointing device 20, of presentation device 25 or of basestation 30) and the plane in which projection region 60 lies. The usermay be queried to align pointing device 20, presentation device 25 orbase station 30 such that the distance measuring device is orientedsubstantially perpendicularly to projection region 60. It should beunderstood that other types of sensors may be included in pointingdevice 20, presentation device 25 or base station 30 to help constrainthe position and/or orientation of interaction structure 72.

In some cases it may be unnecessary to provide a separately embodiedbase station 30. For example, coordinate sensing device 201 may partlyor completely rely on inertial sensing means such as accelerometers andgyroscopes, or on distance measurements with respect to walls, ceilingand/or floor. In such cases it would be possible to leave out basestation 30 entirely and simply choose an appropriate x y z coordinatesystem. In such embodiments communication and control device 204 couldbe configured to communicate directly with the computer.

The present invention also contemplates the use of automated proceduresto establish the nature of the calibration points 721 a, 721 b, 721 c,721 d, based on the measurements of the orientation and/or position ofthe pointing lines 21 that substantially pass through them. For example,with reference to FIG. 7, calibration points 721 a and 721 d need not beexplicitly identified to the user as upper-right and lower-left cornerrespectively, but may merely be identified as diagonally oppositecorners. Those skilled in the art will appreciate that in such a case anautomated procedure may use the measurements of orientation and/orposition of both pointing lines 21, specifically with respect to thex-y-plane, to identify which of the two lines passes through the upperone of the two diagonally opposite corners. The practical consequence tothe user is that the user need not be concerned about which of the twocalibration points 721 a and 721 d is highlighted first. Similararguments can be used to construct automated procedures that determinewhether a pointing line 21 substantially passes through a left or aright corner of interaction region 71 (and, by assumption, ofinteraction structure 72). For example, the a-priori assumption may bemade that the clock-wise angle between a pointing line 21 through a leftcorner and a pointing line 21 through a right corner, measured parallelto the x-y-plane, should not exceed 180 degrees, as will be appreciatedby those skilled in the art.

Finally, although the methods disclosed by the present invention aredescribed in 3D, the invention may also be applied in 2D scenarios.

While the invention has been described with respect to a limited numberof embodiments, those skilled in the art, having benefit of thisdisclosure, will appreciate that other embodiments can be devised whichdo not depart from the scope of the invention as disclosed herein.Accordingly, the scope of the invention should be limited only by theattached claims.

1. A method for controlling a parameter related to a position of acomputer display cursor based on a point-of-aim of a pointing devicewithin an interaction region, comprising: projecting an image of acomputer display to create the interaction region; establishing at leastone calibration point having a predetermined relation to saidinteraction region; directing a pointing line to substantially passthrough said calibration point while measuring a position of and anorientation of the pointing device, said pointing line having apredetermined relationship to said pointing device; and controlling theparameter related to the position of the cursor within the interactionregion using measurements of the position of and the orientation of thepointing device.
 2. The method of claim 1, further comprising:initializing boundaries of the interaction region to substantiallycoincide with a predetermined interaction structure and formulating adescription of said interaction structure, whereby said description maybe used to constrain a position of at least a second calibration point.3. The method according to claim 2, wherein said description uses themeasurements of orientation and position of the pointing device fromsaid measuring at said calibration point.
 4. The method according toclaim 3, wherein said interaction structure is a rectangle, and whereina side of said interaction structure has a predetermined relation to adevice used to, measure the orientation and position of the pointingdevice.
 5. A method for controlling a parameter related to position of acursor on a projected computer screen image, comprising: measuring anangle between a pointing line and a first line, said first line beingrelated in a predetermined way to at least one of Earth's magnetic fielddirection and Earth's gravity field direction, and said pointing linehaving a predetermined relation to a pointing device; using a parameterrelated to the measured angle to control the parameter of said cursor onsaid computer screen image.
 6. The method of claim 5, furthercomprising: first measuring the angle between said pointing line andsaid first line, said pointing line having a predetermined relation to apoint-of-aim; establishing a calibration point, said calibration pointhaving a predetermined relation to said computer screen image; directingsaid pointing line to substantially pass through said calibration pointwhile second measuring the angle between said pointing line and saidfirst line; using the first measured angle and the second measured angleto constrain a parameter related to said point-of-aim whereby the cursorparameter is controlled by position of said point-of-aim measuredrelative to said projected computer screen image.
 7. The method of claim6, further comprising: initializing calculated positions of boundariesof the projected image to substantially coincide with a scaled andparallel version of a predetermined interaction structure; andformulating a description of said interaction structure relative to acoordinate system, said coordinate system having a predeterminedrelation to said first line, whereby said description may be used toconstrain a coordinate of an intersection point, said intersection pointbeing common to said pointing line during said first measuring and saidpredetermined interaction structure.
 8. The method of claim 7, whereinsaid interaction structure is a rectangle, and wherein a side of saidinteraction structure has a predetermined relation to said first line.9. A method for controlling a computer display cursor in an interactionregion, comprising: establishing a calibration point having apredetermined relation to said interaction region; first measuring atleast one of a position and orientation of a pointing line whiledirecting said pointing line to substantially pass through saidcalibration point, the first measurement used to constrain a parameterof said calibration point, the pointing line having a predeterminedrelationship to at least one of position and orientation of a pointingdevice; using a characteristic feature of said interaction region toestablish a property of a common point of said pointing line and saidinteraction region measured relative to said interaction region;measuring at least one of position and orientation of the pointingdevice; and using the characteristic feature of said interaction regionand measurement of the pointing device to control the cursor on acomputer display image.
 10. The method of claim 9 wherein saidcharacteristic feature includes at least one of a position coordinate ofsaid calibration point, a size attribute of said interaction region, ashape of said interaction region, an orientation coordinate of a linethat has a predetermined relation to said interaction region, a positioncoordinate of a point on a line that has a predetermined relation tosaid interaction region, an orientation coordinate of a plane that has apredetermined relation to said interaction region and a positioncoordinate of a point on a plane that has a predetermined relation tosaid interaction region.
 11. The method of claim 9, further comprisingconstraining a coordinate of a point-of-aim of said pointing device,measured relative to said interaction region, said point-of-aimsubstantially lying on said pointing line, the constraining comprising:second measuring the at least one of a position of a point of and anorientation of said pointing line and using the second measurement ofsaid pointing line and the first measurement of said pointing line toconstrain the coordinate of said point-of-aim, whereby said firstmeasurement is used to constrain the coordinate of said point-of-aimrelative to said interaction region.
 12. The method according to claim11, further comprising: initializing said interaction region to have apredetermined relationship with a predetermined interaction structure;and formulating a description of said interaction structure, wherebysaid description is used to constrain a parameter of said point-of-aimrelative to said interaction region.
 13. The method according to claim12, further comprising: combining said description of said interactionstructure with the first measurement of said pointing line and saidsecond measurement of said pointing line to constrain a coordinate of anintersection point of said pointing line and said interaction structureduring said second measurement.
 14. The method according to claim 13,further comprising controlling said cursor on said computer displayimage based on the relation between said intersection point and saiddescription of said interaction structure.
 15. The method of claim 9,further comprising directionally recording vocalization from at leastone viewer of the interaction region, the directionally recording beingsubstantially coaxial with the orientation of the pointing device.
 16. Amethod for controlling a parameter related to position of a cursor on acomputer screen image, comprising: measuring a first angle between apointing line and a first line; measuring a second angle between saidpointing line and a second line, said first line being related in apredetermined way to a geographic reference, said second line beingrelated in a predetermined way to a geographic reference, said pointingline having a predetermined relation to said pointing device, and usinga first parameter related to the first angle, and a second parameterrelated to the second angle to control the parameter of said cursor onsaid computer screen image, whereby said cursor position parameter iscontrolled by movement of said pointing device.
 17. The method of claim16, further comprising constraining a parameter of a point-of-aim ofsaid pointing device with respect to an interaction region, theconstraining comprising: first measuring the first angle and the secondangle wherein said pointing line has a predetermined relation to saidpoint-of-aim; establishing a calibration point having a predeterminedrelation to said interaction region; second measuring the first angleand the second angle while directing said pointing line to substantiallypass through said calibration point; and using the first measurement andthe second measurement of said first and second angles to constrain thecoordinate of said point-of-aim, whereby the parameter of said cursor onsaid computer screen image is controlled by the parameter of saidpoint-of-aim measured relative to said interaction region.
 18. Themethod according to claim 17, further comprising: initializing theinteraction region to be a substantially parallel and scaled version ofa predetermined interaction structure; and formulating a description ofsaid interaction structure relative to at least one of said first lineand said second line, whereby said description is used to constrain acoordinate of an intersection point common to said pointing line duringsaid first measuring and said predetermined interaction structure. 19.The method of claim 18, wherein the formulating said description usesthe first angle between said second measuring of said pointing line andsaid first line and the second angle between said second measuring ofsaid pointing line and said second line.
 20. The method of claim 19,wherein said interaction structure is a rectangle, and wherein a side ofsaid interaction structure has a predetermined relation to at least oneof the first line and the second line.
 21. The method of claim 16wherein the geographic reference for the first line is one of Earth'smagnetic field direction and Earth's gravity field direction, and thegeographic reference for the second line is one of Earth's magneticfield direction and Earth's gravity field direction.